Sorry for jumping in and answering a question not addressed to me. 
That's a long cable. Quality looks OK but 10m is a long run. Do you get the same problems using the short cable supplied with Q10 Pro?
Yes internal player is 'mediaplayer' on home screen. It's also the player that's called by the wrapper in Kodi.
@futeko
Thank you for the time you've dedicated in give to me some hint.
1) This afternoon i'll try with a shorter cable (the supplied one).
2) Ok. Now it's clear to me that "Mediaplayer" on home screen is the same player that's called by the wrapper in Kodi.
3) Yesterday night i'll try using directly the internal player without using Kodi and it works. No problem every 1' 25'' as previous.
I could watch an entire film 4k 23,976 fps 8 bit with my JVC X7000. Amazing picture quality.
4) So at the end of the film i try to make some other test with other 4k files..and after some test it happen again.
I noticed a thing that could be the problem...
When the problem of loosing sync begin the JVC X7000 see every file as it were 10 bit also if it's only 8 bit ...
I play again a short piece of the film i saw a few moment earlier and pushing the "info" button in the JVC X7000 it states that the file was 10 bit color..
but i'm sure and "MediaInfo" in my laptop too that the file is 8 bit.
Upon your opinion this could be the reason of the problem...?
thank you to everyone.
JVC-X7000.