It is rather large, and currently incomplete. The problem is, without any idea of where the error is coming from, it is difficult to know where to start trying to whittle down the code for posting.

Worse is that I am not even sure when it first started appearing as it appears in the middle of several hundred lines of test output. If I hadn't paused the screen at exactly the right moment, I might never have seen it.

I'll try to rationalise the code to something postable, but any clues as to where to start would be useful.