Exception #0 (Exception): Item (Magento\Wishlist\Model\Item) with the same ID "9980" already exists.

### Preconditions
1. Magento 1 ver. 1.9.4.4 with PHP 5.6
2. Magento 2 ver. 2.3.5-p2 with PHP 7.3

### Steps to reproduce
1. Install Migration tool
2. Migrate settings
3. Migrate Data
4. Login into a customer account
5. Add a product to the wishlist

### Expected result
Adding products to the wishlist should work without any errors

### Actual result
After clicking on "Add to wishlist", I'm getting this error `(Exception): Item (Magento\Wishlist\Model\Item) with the same ID "9980" already exists.`

```
1 exception(s):
Exception #0 (Exception): Item (Magento\Wishlist\Model\Item) with the same ID "9980" already exists.

Exception #0 (Exception): Item (Magento\Wishlist\Model\Item) with the same ID "9980" already exists.

#1 Magento\Framework\Data\Collection\AbstractDb->loadWithFilter(false, false) called at [vendor/magento/framework/Data/Collection/AbstractDb.php:565]

#2 Magento\Framework\Data\Collection\AbstractDb->load() called at [vendor/magento/framework/Data/Collection.php:849]

#3 Magento\Framework\Data\Collection->count() called at [vendor/magento/module-wishlist/Model/Wishlist.php:634]

#4 Magento\Wishlist\Model\Wishlist->getItemsCount() called at [vendor/magento/module-wishlist/Block/AbstractBlock.php:276]

#5 Magento\Wishlist\Block\AbstractBlock->getWishlistItemsCount() called at [generated/code/Magento/Wishlist/Block/Customer/Wishlist/Interceptor.php:297]

#6 Magento\Wishlist\Block\Customer\Wishlist\Interceptor->getWishlistItemsCount() called at [vendor/magento/module-wishlist/Block/AbstractBlock.php:301]

#7 Magento\Wishlist\Block\AbstractBlock->hasWishlistItems() called at [generated/code/Magento/Wishlist/Block/Customer/Wishlist/Interceptor.php:323]

#8 Magento\Wishlist\Block\Customer\Wishlist\Interceptor->hasWishlistItems() called at [vendor/magento/module-wishlist/view/frontend/templates/view.phtml:20]

#9 include('/home/mage2theru...') called at [vendor/magento/framework/View/TemplateEngine/Php.php:59]

#10 Magento\Framework\View\TemplateEngine\Php->render(&Magento\Wishlist\Block\Customer\Wishlist\Interceptor#000000001c63723e0000000019db5330#, '/home/mage2theru...', array('csp' => &Magento\Csp\Helper\InlineUtil#000000001c6365c20000000019db5330#)) called at [vendor/magento/framework/Interception/Interceptor.php:58]

#11 Magento\Framework\View\TemplateEngine\Php\Interceptor->___callParent('render', array(&Magento\Wishlist\Block\Customer\Wishlist\Interceptor#000000001c63723e0000000019db5330#, '/home/mage2theru...', array('csp' => &Magento\Csp\Helper\InlineUtil#000000001c6365c20000000019db5330#))) called at [vendor/magento/framework/Interception/Interceptor.php:138]

#12 Magento\Framework\View\TemplateEngine\Php\Interceptor->Magento\Framework\Interception\{closure}(&Magento\Wishlist\Block\Customer\Wishlist\Interceptor#000000001c63723e0000000019db5330#, '/home/mage2theru...', array()) called at [vendor/magento/framework/Interception/Interceptor.php:153]

#13 Magento\Framework\View\TemplateEngine\Php\Interceptor->___callPlugins('render', array(&Magento\Wishlist\Block\Customer\Wishlist\Interceptor#000000001c63723e0000000019db5330#, '/home/mage2theru...', array()), array(array('csp_helper_plugi...'))) called at [generated/code/Magento/Framework/View/TemplateEngine/Php/Interceptor.php:26]

#14 Magento\Framework\View\TemplateEngine\Php\Interceptor->render(&Magento\Wishlist\Block\Customer\Wishlist\Interceptor#000000001c63723e0000000019db5330#, '/home/mage2theru...', array()) called at [vendor/magento/framework/View/Element/Template.php:271]

#15 Magento\Framework\View\Element\Template->fetchView('/home/mage2theru...') called at [generated/code/Magento/Wishlist/Block/Customer/Wishlist/Interceptor.php:726]

#16 Magento\Wishlist\Block\Customer\Wishlist\Interceptor->fetchView('/home/mage2theru...') called at [vendor/magento/framework/View/Element/Template.php:301]

#17 Magento\Framework\View\Element\Template->_toHtml() called at [vendor/magento/module-wishlist/Block/Customer/Wishlist.php:275]

#18 Magento\Wishlist\Block\Customer\Wishlist->_toHtml() called at [vendor/magento/framework/View/Element/AbstractBlock.php:1100]

#19 Magento\Framework\View\Element\AbstractBlock->Magento\Framework\View\Element\{closure}() called at [vendor/magento/framework/View/Element/AbstractBlock.php:1104]

#20 Magento\Framework\View\Element\AbstractBlock->_loadCache() called at [vendor/magento/framework/View/Element/AbstractBlock.php:674]

#21 Magento\Framework\View\Element\AbstractBlock->toHtml() called at [generated/code/Magento/Wishlist/Block/Customer/Wishlist/Interceptor.php:1051]

#22 Magento\Wishlist\Block\Customer\Wishlist\Interceptor->toHtml() called at [vendor/magento/framework/View/Layout.php:566]

#23 Magento\Framework\View\Layout->_renderBlock('customer.wishlis...') called at [vendor/magento/framework/View/Layout.php:542]

#24 Magento\Framework\View\Layout->renderNonCachedElement('customer.wishlis...') called at [generated/code/Magento/Framework/View/Layout/Interceptor.php:206]

#25 Magento\Framework\View\Layout\Interceptor->renderNonCachedElement('customer.wishlis...') called at [vendor/magento/framework/View/Layout.php:497]

#26 Magento\Framework\View\Layout->renderElement('customer.wishlis...', false) called at [generated/code/Magento/Framework/View/Layout/Interceptor.php:193]

#27 Magento\Framework\View\Layout\Interceptor->renderElement('customer.wishlis...', false) called at [vendor/magento/framework/View/Layout.php:594]

#28 Magento\Framework\View\Layout->_renderContainer('content', false) called at [vendor/magento/framework/View/Layout.php:544]

#29 Magento\Framework\View\Layout->renderNonCachedElement('content') called at [generated/code/Magento/Framework/View/Layout/Interceptor.php:206]

#30 Magento\Framework\View\Layout\Interceptor->renderNonCachedElement('content') called at [vendor/magento/framework/View/Layout.php:497]

#31 Magento\Framework\View\Layout->renderElement('content', false) called at [generated/code/Magento/Framework/View/Layout/Interceptor.php:193]

#32 Magento\Framework\View\Layout\Interceptor->renderElement('content', false) called at [vendor/magento/framework/View/Layout.php:594]

#33 Magento\Framework\View\Layout->_renderContainer('main', false) called at [vendor/magento/framework/View/Layout.php:544]

#34 Magento\Framework\View\Layout->renderNonCachedElement('main') called at [generated/code/Magento/Framework/View/Layout/Interceptor.php:206]

#35 Magento\Framework\View\Layout\Interceptor->renderNonCachedElement('main') called at [vendor/magento/framework/View/Layout.php:497]

#36 Magento\Framework\View\Layout->renderElement('main', false) called at [generated/code/Magento/Framework/View/Layout/Interceptor.php:193]

#37 Magento\Framework\View\Layout\Interceptor->renderElement('main', false) called at [vendor/magento/framework/View/Layout.php:594]

#38 Magento\Framework\View\Layout->_renderContainer('columns', false) called at [vendor/magento/framework/View/Layout.php:544]

#39 Magento\Framework\View\Layout->renderNonCachedElement('columns') called at [generated/code/Magento/Framework/View/Layout/Interceptor.php:206]

#40 Magento\Framework\View\Layout\Interceptor->renderNonCachedElement('columns') called at [vendor/magento/framework/View/Layout.php:497]

#41 Magento\Framework\View\Layout->renderElement('columns', false) called at [generated/code/Magento/Framework/View/Layout/Interceptor.php:193]

#42 Magento\Framework\View\Layout\Interceptor->renderElement('columns', false) called at [vendor/magento/framework/View/Layout.php:594]

#43 Magento\Framework\View\Layout->_renderContainer('main.content', false) called at [vendor/magento/framework/View/Layout.php:544]

#44 Magento\Framework\View\Layout->renderNonCachedElement('main.content') called at [generated/code/Magento/Framework/View/Layout/Interceptor.php:206]

#45 Magento\Framework\View\Layout\Interceptor->renderNonCachedElement('main.content') called at [vendor/magento/framework/View/Layout.php:497]

#46 Magento\Framework\View\Layout->renderElement('main.content', false) called at [generated/code/Magento/Framework/View/Layout/Interceptor.php:193]

#47 Magento\Framework\View\Layout\Interceptor->renderElement('main.content', false) called at [vendor/magento/framework/View/Layout.php:594]

#48 Magento\Framework\View\Layout->_renderContainer('page.wrapper', false) called at [vendor/magento/framework/View/Layout.php:544]

#49 Magento\Framework\View\Layout->renderNonCachedElement('page.wrapper') called at [generated/code/Magento/Framework/View/Layout/Interceptor.php:206]

#50 Magento\Framework\View\Layout\Interceptor->renderNonCachedElement('page.wrapper') called at [vendor/magento/framework/View/Layout.php:497]

#51 Magento\Framework\View\Layout->renderElement('page.wrapper', false) called at [generated/code/Magento/Framework/View/Layout/Interceptor.php:193]

#52 Magento\Framework\View\Layout\Interceptor->renderElement('page.wrapper', false) called at [vendor/magento/framework/View/Layout.php:594]

#53 Magento\Framework\View\Layout->_renderContainer('root', false) called at [vendor/magento/framework/View/Layout.php:544]

#54 Magento\Framework\View\Layout->renderNonCachedElement('root') called at [generated/code/Magento/Framework/View/Layout/Interceptor.php:206]

#55 Magento\Framework\View\Layout\Interceptor->renderNonCachedElement('root') called at [vendor/magento/framework/View/Layout.php:497]

#56 Magento\Framework\View\Layout->renderElement('root', true) called at [generated/code/Magento/Framework/View/Layout/Interceptor.php:193]

#57 Magento\Framework\View\Layout\Interceptor->renderElement('root') called at [vendor/magento/framework/View/Layout.php:963]

#58 Magento\Framework\View\Layout->getOutput() called at [vendor/magento/framework/Interception/Interceptor.php:58]

#59 Magento\Framework\View\Layout\Interceptor->___callParent('getOutput', array()) called at [vendor/magento/framework/Interception/Interceptor.php:138]

#60 Magento\Framework\View\Layout\Interceptor->Magento\Framework\Interception\{closure}() called at [vendor/magento/framework/Interception/Interceptor.php:153]

#61 Magento\Framework\View\Layout\Interceptor->___callPlugins('getOutput', array(), array(array('layout-model-cac...'))) called at [generated/code/Magento/Framework/View/Layout/Interceptor.php:494]

#62 Magento\Framework\View\Layout\Interceptor->getOutput() called at [vendor/magento/framework/View/Result/Page.php:258]

#63 Magento\Framework\View\Result\Page->render(&Magento\Framework\App\Response\Http\Interceptor#000000001c6378500000000019db5330#) called at [vendor/magento/framework/View/Result/Layout.php:171]

#64 Magento\Framework\View\Result\Layout->renderResult(&Magento\Framework\App\Response\Http\Interceptor#000000001c6378500000000019db5330#) called at [vendor/magento/framework/Interception/Interceptor.php:58]

#65 Magento\Framework\View\Result\Page\Interceptor->___callParent('renderResult', array(&Magento\Framework\App\Response\Http\Interceptor#000000001c6378500000000019db5330#)) called at [vendor/magento/framework/Interception/Interceptor.php:138]

#66 Magento\Framework\View\Result\Page\Interceptor->Magento\Framework\Interception\{closure}(&Magento\Framework\App\Response\Http\Interceptor#000000001c6378500000000019db5330#) called at [vendor/magento/framework/Interception/Interceptor.php:153]

#67 Magento\Framework\View\Result\Page\Interceptor->___callPlugins('renderResult', array(&Magento\Framework\App\Response\Http\Interceptor#000000001c6378500000000019db5330#), array(array('result-messages', 'result-builtin-c...', 'result-varnish-c...'))) called at [generated/code/Magento/Framework/View/Result/Page/Interceptor.php:130]

#68 Magento\Framework\View\Result\Page\Interceptor->renderResult(&Magento\Framework\App\Response\Http\Interceptor#000000001c6378500000000019db5330#) called at [vendor/magento/framework/App/Http.php:120]

#69 Magento\Framework\App\Http->launch() called at [generated/code/Magento/Framework/App/Http/Interceptor.php:24]

#70 Magento\Framework\App\Http\Interceptor->launch() called at [vendor/magento/framework/App/Bootstrap.php:261]

#71 Magento\Framework\App\Bootstrap->run(&Magento\Framework\App\Http\Interceptor#000000001c63784b0000000019db5330#) called at [index.php:39]

### Additional notes
- There is an already opened issue on the Magento main repo https://github.com/magento/magento2/issues/27137 but I opened this issue here because I got this error after migrating from M1

- I also tried to truncate these tables `wishlist`, `wishlist_item` & `wishlist_item_option` and I got the same error `Exception #0 (Exception): Item (Magento\Wishlist\Model\Item) with the same ID "1" already exists.`

Reproduce the migration and wishlist flow described in the issue, then start at vendor/magento/framework/Data/Collection/AbstractDb.php:565 and vendor/magento/module-wishlist/Model/Wishlist.php:634 from the stack trace. Trace why the migrated wishlist collection contains duplicate item ID 9980; done means adding a product to the wishlist completes without the duplicate-ID exception.

Written by the indexing model from the issue text.