Ok, so combined with this bug (https://forum.pspad.com/read.php?4,78269,78278),
it seems like 0x00ff is randomly being written to the heap.

I know this isn't an open-source project, but as you can't reproduce the
problem, Jan, I'd like offer to try and debug it for you, if you would be happy
to privately share the source/project. Hopefully should just be able to set a
watchpoint on the strings on the heap to find out where the write is coming

PSPad freeware editor https://www.pspad.com

Odpovedet emailem