Performance issues with multiple instances (massive lag and app freezes)

Check version

• I'm running the latest version of Path of Building and I've verified this by checking the changelog

Check for duplicates

• I've checked for duplicate issues by using the search function of the issue tracker

What is the expected behaviour/value?

• The app should not start lagging and freeze like crazy when you open a second instance (otherwise prevent it).
• It should ideally share resources with the 1st one (looks fine, although it a bit heavy on RAM ~400mb each).
• I should be able to search for a gem in the skills menu without a 3 seconds freeze (not responding).
• I should be able to select / unselect nodes on the tree without lag or freezes

What is the actual behaviour/value?

When two instances of PoB are running :

• Selecting / unselecting a node (even worst when pathfinding comes up for mulitple nodes) it lag massively and often freezes for 1-2 seconds
• Searching for a gem in the Skills menu should not freeze the app for 3+ seconds
• Selecting an item in the dropdown in the Items menu should not freeze or lag the app
• Creating a new item in the Items menu, should not freeze the app for 1 second after clicking save

Seems like PoB is re-calculating / doing backend stuff on the UI thread most of the time, which cause massive lag and freeze, with a medium / full size tree.

How to reproduce the issue

After opening one (or both) the following PoB codes below in two instances of PoB :

• Select / unselect nodes in the Tree menu (should notice lag or freeze)
• Search for a gem in the dropdown of the Skills menu (should notice freeze)
• Try changing the select item in one slot of the Item menu (should notice lag or freeze)

Character build code

#1 is from a build guide : https://pastebin.com/w0krs09Q
#2 is from one of my character's profile : https://pastebin.com/Eg6AtanZ

But, it lag with any medium / full size trees I've used.

Screenshots

No response

Start by reproducing the freezes with two Path of Building instances and the supplied PoB codes, focusing on the Tree, Skills, and Items menus. Compare node selection, gem searches, item selection, and item creation between one and two instances; done means these interactions no longer cause the reported lag or freezes.