I suspect this issue might be related to Cardmark debuffs(not a savefile corruption), so does this happen when you're fighting with strong enemies on the first stage?
I fixed it :)
going to fix the knife effect bug & the thing you talked (mod and etc thing affection on the reward scene) is more of a specification than a bug. in that scene I didn't set any synced save for the cards & I just make card preivew for just and preview purpose, not for edit. but as you said I totaly forgot can put the cardmark items on there... well so I need to fix it...
i'll post an update after I fixed it all!
sorry for confusing... in knife deleting part you need to drag & drop 10 knife skills that you already own(the things on the right is the placeholder for delete). When you filled all of the blank on the right side , you can now press the rebirth button. (I checked the part of the system is not made well and causing a trouble so fix I'm working on it to fix & I think I need to improve the UI on the part so will do it together)