I have hit what appears to be a "YouTube TV" (vs YouTube) buffering problem. It happens only with Firefox on my PCs. After a few seconds to a minute of playing a TV program or movie, the video/audio stops with a spinning arrow. If I previously had turned on "stats for nerds" to monitor this, I can see when network activity stops and the buffer then eventually gets exhausted. This does NOT happen when running YouTube TV on my TVs or on my iPhone. Probably more significant, it does NOT happen with YouTube TV under either Microsoft Edge or Google Chrome on these PCs. If I run Firefox in Troubleshoot Mode, i.e., no add-ons, extensions, etc., the problem still exists, so it is not just some rogue add-on, but is related to Firefox itself. The problem appears to be only for "YouTube TV" on Firefox since, for example, videos played from YouTube (vs "YouTube TV") do not have the problem under Firefox. I tried rebooting my router as well as the PCs. The problem still existed. The PCs are high speed and the internet connection is fiber optic. One of the PCs is connected by Ethernet; the other is wireless. Download/upload speeds are over 900 Mbps on the Ethernet PC. I have not seen slow network indications on anything except this "YouTube TV" with Firefox mixture. Hardware does not seem to be the issue. Apparently the problem is software. I also tried temporarily disabling my antivirus/firewall software. No change. I'm running Windows 10 version 21H1 and Firefox 88.0.1. I'm new to YouTube TV; although most of my viewing with it has been done on TVs, I don't recall seeing this problem in my PC tests a month or so ago.