Same issue here….. incredibly frustrating!!! Has been this way for nearly 2 years for me and I just accepted it at first, but having discovered this thread and realised it is a common issue, want to get this finally resolved! The Vimeo plus embedded video on the landing cover page of website starts blurry for 5-8 seconds and makes it look really unprofessional . It doesn’t have anything to do with bad internet speed or video size (which in this instance is small & short in time).
Has anyone discovered a solution or a workaround yet? Has anyone had any luck after contacting Squarespace Customer Support either?