Default [Q] Youtube not working after a while


I recently purchased a silver HTC One 32GB (european version with LTE). I S-OFF-ed it and installed the rooted version of "[RUU] Google Edition Conversion. 4.4 RUU Zip pre-rooted/non-rooted + Firmware".
The problem is that youtube stops working after a while (both in youtube application and in chrome). Basically no video plays anymore. Every other functionality works fine except playing videos. Chrome tries to play the video but it says "This video cannot be played". If I try again in Chrome, it simply closes (I guess it crashes). Youtube application just shows the loading animation (on the black background) and just sits there indefinitely. Mx Player works fine with videos stored on the phone (I guess it uses it's own codecs).
Rebooting the phone makes youtube to work again (sometimes) but after a while it stops working again.
I would've posted on "[RUU] Google Edition Conversion. 4.4 RUU Zip pre-rooted/non-rooted + Firmware" thread, but I have less than 10 posts.

Any idea what the problem is or how could I overcome it? I also tried factory reset, clearing cache/data, etc. Nothing works, it does the same thing. I also searched and couldn't find anyone with a similar problem like me.

I don't know if the original firmware was working well because I didn't use it more than 1 hour (I must say I like the stock android experience).