Wow, that was fast. You guys are awesome, thanks!
When I say 'per tick' I mean that every frame I append numbers - which identify current input - to a text file. Later I can read that file and have the game simulate the input that was down in each frame, in order, as if I was playing the game and doing the exact same thing.
When I say 'Minimumframerate', I'm referring to a system expression which caps deltatime - so I can use it to make my game framerate dependent and do more precise stuff like this.
I hadn't considered timestamping it, that is an excellent idea, yes. I'll let you know how that turns out. Thanks for the quick response!
I've set it to 99999 because, when set to 60, displaying "dt" every tick shows a value which changes slightly per frame, which I thought could be the cause of the problem. I've tried again with 60 just to be sure, and still get the same results.
The changes are quite slight, so it can be hard to notice if you only have a sprite moving around on its own. My game has moving platforms and hazards, which can make a tiny difference mean a lot more.
Would you mind sending your capx so I can compare the way you did it with mine and see if I've done something silly? Thanks for helping out so quickly!