`OCP\Files\NotPermittedException` `Could not create folder`

I had a similar issue with Nextcloud 22.2.4:

2022-02-06T10:01:50+00:00 In Folder.php line 173:
2022-02-06T10:01:50+00:00                                         
2022-02-06T10:01:50+00:00   [OCP\Files\NotPermittedException]     
2022-02-06T10:01:50+00:00   Could not create folder: {$fullPath}  
2022-02-06T10:01:50+00:00                                         
2022-02-06T10:01:50+00:00 
2022-02-06T10:01:50+00:00 Exception trace:
2022-02-06T10:01:50+00:00   at /var/www/html/lib/private/Files/Node/Folder.php:173
2022-02-06T10:01:50+00:00  OC\Files\Node\Folder->newFolder() at /var/www/html/lib/private/Files/AppData/AppData.php:156
2022-02-06T10:01:50+00:00  OC\Files\AppData\AppData->newFolder() at /var/www/html/lib/private/Preview/Storage/Root.php:74
2022-02-06T10:01:50+00:00  OC\Preview\Storage\Root->newFolder() at /var/www/html/lib/private/Preview/Generator.php:472
2022-02-06T10:01:50+00:00  OC\Preview\Generator->getPreviewFolder() at /var/www/html/lib/private/Preview/Generator.php:132
2022-02-06T10:01:50+00:00  OC\Preview\Generator->generatePreviews() at /var/www/html/lib/private/PreviewManager.php:204
2022-02-06T10:01:50+00:00  OC\PreviewManager->generatePreviews() at /var/www/html/custom_apps/previewgenerator/lib/Command/Generate.php:243
2022-02-06T10:01:50+00:00  OCA\PreviewGenerator\Command\Generate->parseFile() at /var/www/html/custom_apps/previewgenerator/lib/Command/Generate.php:214
2022-02-06T10:01:50+00:00  OCA\PreviewGenerator\Command\Generate->parseFolder() at /var/www/html/custom_apps/previewgenerator/lib/Command/Generate.php:212
2022-02-06T10:01:50+00:00  OCA\PreviewGenerator\Command\Generate->parseFolder() at /var/www/html/custom_apps/previewgenerator/lib/Command/Generate.php:212
2022-02-06T10:01:50+00:00  OCA\PreviewGenerator\Command\Generate->parseFolder() at /var/www/html/custom_apps/previewgenerator/lib/Command/Generate.php:212
2022-02-06T10:01:50+00:00  OCA\PreviewGenerator\Command\Generate->parseFolder() at /var/www/html/custom_apps/previewgenerator/lib/Command/Generate.php:183
2022-02-06T10:01:50+00:00  OCA\PreviewGenerator\Command\Generate->generatePathPreviews() at /var/www/html/custom_apps/previewgenerator/lib/Command/Generate.php:131
2022-02-06T10:01:50+00:00  OCA\PreviewGenerator\Command\Generate->execute() at /var/www/html/3rdparty/symfony/console/Command/Command.php:255
2022-02-06T10:01:50+00:00  Symfony\Component\Console\Command\Command->run() at /var/www/html/3rdparty/symfony/console/Application.php:1009
2022-02-06T10:01:50+00:00  Symfony\Component\Console\Application->doRunCommand() at /var/www/html/3rdparty/symfony/console/Application.php:273
2022-02-06T10:01:50+00:00  Symfony\Component\Console\Application->doRun() at /var/www/html/3rdparty/symfony/console/Application.php:149
2022-02-06T10:01:50+00:00  Symfony\Component\Console\Application->run() at /var/www/html/lib/private/Console/Application.php:209
2022-02-06T10:01:50+00:00  OC\Console\Application->run() at /var/www/html/console.php:99
2022-02-06T10:01:50+00:00  require_once() at /var/www/html/occ:11

I added a log output in
nextcloud/lib/private/Files/Node/Folder.php:173:
throw new NotPermittedException('Could not create folder, fullPath: '.$fullPath.', path: '.$path);

After i checked and the folder did exist for me. So to fix this i added a check on the creation if the folder already exists to fix this and changed it to:
if (!$this->get($path) || !$this->view->mkdir($fullPath)) { throw new NotPermittedException('Could not create folder, fullPath: '.$fullPath.', path: '.$path); }

Originally posted by @f4t-t0ny in https://github.com/nextcloud/previewgenerator/issues/121#issuecomment-1030803305

Start in lib/private/Files/Node/Folder.php at line 173 and trace the folder creation calls shown through lib/private/Preview/Storage/Root.php and lib/private/Preview/Generator.php. Compare the reported existing-folder condition with the previewgenerator command paths in lib/Command/Generate.php, then verify that the error is no longer raised incorrectly when the folder already exists.