multislide videos "get crazy" (go back and forth on hisown initiative)

I am massively using multislide syncronized videos and facing a BIG issue.

When I preview or publish the cp7 project, some videos "get crazy".

In particular a repeats short parts of itself (especially where there is the slide change, or especially when I move back and forth through the slides). 
After many tests it seems that this "phenomenon" takes place when I publish in SWF only, not in HTML5.
Please help me, my project is stopped.