[GraemeJ]

Yes, I disabled the debounce but it made no difference.

Hmmm ... I would think, all things considered, disabling the de-bounce is the last thing you should be doing. If anything, try increasing the period (although mine is set on 1/4 second and works well).

Virtually all mechanical switches exhibit contact bounce, to one degree or another, and contact bounce is a prime cause of multiple triggering events.