Just typing comments in Youtube and when pressing the letter "i" it minimizes the window, typing the letter "f" maximizes the window...and so on. Just normal typing is doing this and if you happen to need one of those letters, it cannot be typed and will instead act like a shortcut key and perform the associated function.

Very weird. Tested this with Chrome and Edge, does not have this issue. Restarted computer, did not resolve the issue. Disabled the 3 addons I have - Ublock Origin, Video Downloader and BitWarden and did not resolve the problem. Just started after the latest update this morning - 86.0, says I'm up to date.