Going backward page on Youtube do not work and audio plays twice with a delay

Hi, every time I'm on Youtube it's like Firefox load the page 2 times and when I try to go back o the previous page it reloads the current: For example I play video #1, then I click in another video it opens the video #2 page, if I click the back page button even without playing video #2 it reloads video #2 page. The second problem with Youtube is the audio: sometimes when playing a video suddenly on background it restart the audio of the video and it plays together, and if I pause the video the "first audio" stop but the second keeps going.

Already tried the fix audio solution but nothing changed, also cleared cache etc....