For several days Firefox Nightly has been stopping and backtracking while trying to play videos from YouTube and from a news site called Topnewsshow. com. I mainly listen to these sites pretty much round the clock to keep up with world events, so I don't know if this would happpen for all sites. I've checked the service status of my BT broadband, and the engineers say they have not heard of a fault like mine. Though I did think it must be the line (twisted wire from the fibre box), as I've had trouble with it before, I tried with Chrome, and, not only did it play without stuttering, it actually played at high quality, which has not been possible on Topnewsshow for some time, but I didn't suspect the browser until it started stuttering on YouTube too. It may play for a minute or two and let you think it's working, but then it will jump back and start repeating from about 30s before. It can take an hour to get through a half hour video. It has been driving me nuts. I've tried it on two different phones, one Android 8 and one Android 11, and I've tried clearing the cache, and, eventually, uninstalling, rebooting, and downloading fresh from play store. It is still the same. Firefox has always been problematic on some sites, particularly when trying to complete purchases: often have to switch to Chrome, and never have been able to find why. I use Nightly so that I can use about:config to adjust the zooming settings and pixels per pixel to get the best fits on my unusual aspect ratio keyboard phones (Titan Pocket, Cosmo Communicator), but the fault was the same on the fresh download before adjusting, and adding add ons. While searching for solutions, I read about Firefox forks, and so tried installing Ice Raven on the Cosmo (not installed on the Titan I'm writing this on yet). IceRaven plays the videos without stuttering and in good quality on YouTube. It still has to play at lowest quality on the Topnewsshow site, but it doesn't keep doubling back the way it does on Firefox. Topnewsshow is Russian, so I wasn't expecting top quality, but it has been very handy for me to listen to US news from the UK. It's pretty much unbearable to have to hear people keep doubling back mid sentence, so I've been surprised not to have found anyone else complaining of this effect. Perhaps it is because I tend to listen to longer content and speech rather than music: people who only listen to short clips may not notice the fault.