@chris
xadUnFile is back to crashing with your xad_7z installed again. I consistently get "Exception 6: chk instruction" with PC=$2e. I tried using MuForce but the system freezes when I do with no hits before it does. xad_7z worked the first time I installed it and rebooted but crashes now with the same archive. There's plenty of stack for xadUnFile according to Scout.
I used BDebug to catch a crashed task and it looks like there is a branch to PC=8 first. Back tracking from the last stack entry, I find xad_xfd+$3f0 doing a jsr to exec/OpenLibrary() opening xfdmaster.library version $26. I don't see any problems with the xad_xfd code. Removing xad_7z from Libs:xad/ stops the crashes. I'm surprised no one else has reported this problem. Versions used are...
xadmaster.library 12.1
xad_7z 2.4
xad_xfd 1.1
xadUnFile 1.25
My setup is a 3000T with CSMK3 68060 using AmigaOS 3.9.
xad_xfd 68k version definitely doesn't work, remove it and see if that also stops xad_7z crashing.