I don't recall the fix I used but on another PC it cleared up over time as Flash updated.
I'd not fix but use what works for now and wait for Flash to update.
I'm not actually sure if this is the right forum, so forgive me if it's misplaced! I have a Windows 10 desktop that has very recently started playing back videos strangely. In both Chrome and Microsoft Edge as well as Windows Media Player (but interestingly NOT Firefox), videos will be zoomed way in making them impossible to view. I have checked that my display settings are correct, have made sure my video driver is up-to-date, I have tried to adjust playback quality to see if it did anything and have cleared the cache in Chrome plus reset the browser settings -- all to no avail. Here is a photo so that you can see what I'm talking about. The photo on the left is what I see in Chrome/ME/WMP and on the right, what the video should look like in Firefox.