The topic @3dRaven mentioned, look for this file ‘OrionGlobalGameplayCollection’ and remove it Paragon Characters are Incompatible with 5.4 - #17 by Sebatnik
As for Paragon, these characters per se appear to work just fine, I know this from working and selling edited modular UE4 compatible skeleton versions https://www.unrealengine.com/marketplace/en-US/product/eef4a3e461df406c9e91712edd0721dd