Thank you all SLR folk. I think it is ok now. Tested several videos about one hour and everything works smooth. No out of sync anymore.

I am curious... Can we have some explanation what went wrong and how did you fix it? How do you prevent this does not happen again and is there something to learn about?

    Picouser there is definitely something to learn for us and we are already adjusting our processes.
    Explanation is very simple - we updated video player module internals and missed this regression.
    We appreciate our users and will be more careful during major upgrades.