Got 2 for you:
The core engine runs into conflict with Yanfly's Battle Core causing a crash at the end of the player's turn block is applied with <Card Target Actions>:
https://forums.rpgmakerweb.com/attachments/1779627519935-png.366944/
This seems to be a result of redundancy or conflict with the window message function, and can be at least partly resolved by changing 'this._cardTargetActions = null;' to 'this._cardTargetActions = [];' on line 9096.
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Heavy lag at the end of player turn if multiple party members are present. I can see why this issue would take years to come up.