iOS - app crashes after update, clean install is OK - how to debug this?

I have a problem with one of my apps. I have released major update, that also changed app bundle data and core functionality.

Users, that install this app version as an update, got a startup-crash. Clean installs seems to be correct (at least users with this problem says so, after deleting app and doing clean install, problem is gone).

From Apple crash log, the log is weird, because the stack trace is incorrect. It says, that crash is in method A that is called from B. However, method A is never called from B in my code.

Is there a way how to debug this? Can I somehow install (retrieve) previous version of app and test update with XCode debugger running? I dont have codes for the previous version, so I cannot do its build manually and test it.