Bug?self jumping movieClip at end of loop

hello

I made simple animation with 2 layers, and some frames, nothing special, only 2 movieClips, by one on each layer. Animation is nothing more than manipulating alpha.

And here’s some bug (?):

When the animation ends and backs to the beginnig, movieClip change its x position a little and then backs to right position again. movieClip is jumping once on any repeat.

This problem started when I created motion tween between keyframes. This is happening when I’m testing movie and after publish but everything is allright when i just playing animation in edit mode.

please help.