Small hint needed: how to track down `superclass mismatch for class` bug?

[iRonin]

I've started working with Spring on our existing app and noticed that from time to time I get the superclass mismatch for class bug, mostly for our Interactors. What has been solving it for now is to "undefine" the troublesome class by removing its constant from its parent class. Any hint of what may be going on and how to track it down? Thank you!