Samsung QE55Q6FN constant YouTube buffering

[PowerBuldog]

Hi 

 

I've a Samsung QE55Q6FN. 

Lately when i try to watch any YouTube 4kb content i get the spinning buffering. The buffer health drops to 0.0s after a few seconds. Only 360p works as of now. 

5GHz WiFi with 270mbit speed is present. (1gbit on lan). Netflix has no problem with it, also the browser shows stable 250+mbit with 9ms ping. 

It must be the youtube app on the tv, because there is no problem with YouTube on 2 mobile phone and another Samsung smart tv connected to the same 5ghz network. 

Also youtube works just fine in the built in tv browser. 

 

I've tried to reinstall the app. Logout then login back in. Reset the app to defaults. Nothing helped. 

 

Any suggestions what can be done to it to make it work again?