I have been having a slight on going problem with Firefox lately. Where the PC will freeze with CPU load pegged at 100% for several seconds between watching videos or when an ad pops up while watching a video(normally I run uBlock, but I disabled all add-ons), but this is random and wont happen on at times. I am currently using Waterfox and have 0 issues, but Waterfox is not supported fully for Amazon Prime Video. I have done the common things such as updating to the latest release, reinstalling the browser, refreshing the browser, disabling all add-ons, updated drivers, disabled hardware acceleration, reinstalled windows but the issue does seem to be persistent. Even after a clean install of Windows & an install the latest Firefox the issue cropped up. I did use Firefox's performance recorder to capture When viewing under ""Waterfall"" The main large recorded events are '''DOM Event '''and when expanded has '''Promise Callback''' When viewing under ""Call Tree"" The largest event is '''MediaSource.isTypeSupported''' I did save the recording so it can be viewed as I do not understand the details. I know this is not a hardware issue as I also duel boot LMDE4 and have 0 issues using Firefoxwhen in Linux and ''if'' it were a hardware issue I would expect to have problems in linux as well as when using Waterfox in windows. I have stress tested my GPU and have had 0 issues. I can upload the Performance Recording if needed. My Hardware is. i5 6600K 32GB 3000Mhz RAM GTX1080 1TB NVMe SSD.