I do not know if this will help or complicate the detection of the bug.I had a similar problem (bug) described here:
https://forum.renoise.com/t/bug-cloning-groups-and-collapse-expand-and-others/48254
Maybe the cause is not the same, but the error poster says the same thing: “A fatal error or crash occurred (unhandled exception in thread: GUI)”
BLA BLA BLA ... ... Application: Caught an unhandled fatal exception (Thread: GUI)! Application: Saving a backup...Maybe they are related. The bug that I suffered, I have not been able to reproduce it again. It must be an extraordinary, strange case.This bug was related to the addition or deletion of clues through a tool. I understand that a tool should never close Renoise. If there is an error, an error window appears and closes the tool, not Renoise, unless the code is malicious, to fuck the CPU, and we just do the opposite.
It`s definitely worth noting. I think those errors are pretty standard when the GUI thread gets bungled somehow, and I have possibly had something similar with groups; though I tend to run a lot of VSTs so hard to tell sometimes what did what to what…
I may be doing a small script with the groups soon, so I`ll post up in that thread if I find anything.