I keep having to "forget about this site" for YouTube after watching (admittedly many) videos - every 2 months or so. The tell-tale sign is that videos stutter

I keep having to "forget about this site" for YouTube after watching (admittedly many) videos - every 2 months or so. The tell-tale sign is that videos stutter outrageously. It is surprisingly consistent - stutters / freezes happening, forget about site, problem solved. I would be surprised if this is solely due to Firefox btw; I trust YT-owner Google about as far as I can toss the lot of them.