Computers can seem very illogical and have a mind of their own sometimes, especially when in stressful situations. The fact is that all computers run on software, and software never does anything on its own. It only does anything when it's explicitly told to do so. The instructions can come from a unconscious user interaction, or a glossed over programmer's mistake, the fact remains that there is always an identifiable source of the change. Software never does anything 'by itself'.
Resolume is software, and like all software, it won't suddenly change speed unless it receives instructions to do so. My first hunch is to agree with Ravensc, that you unconsciously changed the Master Speed. You do, in fact, have such a control. You can read more about it here: http://resolume.com/manual/en/r5/compos ... n_controls
Even when that control is not visible and can't be accidentally clicked on, it's very easy to change it via DMX, a forgotten Midi shortcut or a stray command from an OSC interface you downloaded somewhere.
When doing important audio intros, I always make sure to right click both clip speed and master speed before the show moment. Even when I'm positive I didn't change either of those settings. That way I'm 100% sure it will play as it did during practice.