Midi question

[Sizlack]

This may not be the correct forum to post this in...
Anyways, Here's my question/problem. I'm using a nanokey with fruity loops and writing some synths. I don't know if this pertains just to this particular synth but it is confusing me. I have a section done about 4 bars, the same pattern each bar. When I play it back the actual sounds change each play through, weather I let it loop continuously or stop playback and restart from the beginning. Even if I cut out the last 3 and only play one bar it changes each time, the pattern is the same but the sound changes.

I'm still pretty new to all this but feel I have a pretty firm grasp on most of it but this just baffles me.