Greetings, neilwatson.

As I don't have access to your entire script. I feel compelled to ask; are you by chance using warnings, or diagnostics?

Using either one of these should emit a great deal of additional information. That 1) gives you an immediate answer to your question, or 2) gives you some very good clues, as to what to look for, in order to get your answer. :)

Best wishes

--Chris