Sorry to hear that. I’ve just watched a bit of @eastgate’s Vimeo for this meet-up in several places, full screen and not and on different sized monitors and it looks fine. That would suggest your connection to the Vimeo server (somewhere on LAN, broadband connection or internet path to Vimeo.com) is getting slowed down and Vimeo is trying to compensate. Most video streamers now monitor delivery bandwidth and auto-correct the quality of recording passed. If I recall, YouTube does this constantly, in small segments so the quality of transmitted video to rise and fall during the viewing of a single video! This may not be the error, watching the same video while connecting from a different LAN/wi-fi would help sort that.
I don’t believe Vimeo does automatic close captions (or not for free) but there may be some services that would generate an (English transcript) for you, with time codes for cross-reference. I’m in a meeting shortly with some people who know more about captioning so will post back if there are any good resources that might help.