When you do "find last error" and the error _is_ trackable but it is inside some (possibly nested) GOP-enabled subpatch or abstraction, you get this on the console:
Last trackable error:
but the canvas containing the object that caused the error is not opened and nothing is highlighted anywhere, that is, nothing gives any clue of where the error is.
Tested on Windows and Linux, Pd Vanilla 0.42.5.
I reported this 3 years ago, but my description of the issue was confusing and misleading, and the description seems to be the only thing you cannot edit; so I'm creating this new artifact and I'll mark the other one as duplicate of this one.
I will raise the priority because this makes serious development impossible.