Got it sorted after looking at my code for the last 3 hours, my collision detection routine was flagging my sprite as being on a platform (which strictly speaking it was) for a split second while it was touching the side of the platform and moving towards it while also jumping - as soon as it reached a certain point it kicked off the animation briefly before stopping it again as the sprite flew above the platform. It was this that I was seeing - I hadn't put a check in to disable animation at that point if the sprite was in an upward jump motion.
Clearly it's caused by gamma rays interacting adversely with the silicon of your CPU.
It's been a long day - that made me laugh - much needed!!
Yeah sorry, I know it's a really vague question. The problem is I can't post a video of it as the problem doesn't seem to be visible in the video when it's been recorded - even though I can see it clearly with my eyes (on the actual device it's running on)
I'm gonna do as you suggest and try to log out which animation frames are showing and when... might give me some insight into what's happening.
Thanks all, yep my platforms are pretty much flat at the moment, I don't thik I will be introducing slopes at this point - thanks I will probably stick with the constant gravity method as it seems a lot easier to employ than switching between states. Cheers!