Tracking down "Unknown oword" message?

When I abort execution of my programs, Axis pops up "Unknown oword number", but doesn't give me any more context. I've looked at a couple NC files that might've been causing this, but they seem okay.

Is there any way to figure out what it's complaining about?

Seen that once or twice when stopping a running gcode with no owords, but it does not change anything, the machines works as usual so i did not bother with it.
Is this happening on a plasma with PlasmaC?