We're running into exactly the same problem and cannot release another update for our app. Would be really great if somebody from Apple could look into this. We've also created a support case with number 102224346553.

We're also affected by the crash, here's two sample apps that demonstrate it: https://github.com/plu/UITextViewCrash FB16604342 Only happens on iOS 18.4 Beta - any other iOS version before that was fine.