Tablet [Q] Youtube (android) landscape mode problem

Hy guys!

I've got a problem, with my youtube app. In youtube, the video does not rotate to landscape, when the device is in landscape mode. It stays like this:
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I don't know why. But, in the factory YouTube version (4.4.11) there's no problem with it. It rotates well.
My tablet is a Wayteq xtab-70dci. With Jelly Bean 4.2.2. Any ideas?
(sorry for my english)