Blurry thumbnails when linking Vimeo videos to SQSP video page

Hi,

I have previously linked certain Vimeo videos to image "blocks" in various pages on SQSP site.  Video thumbnails were "selected from video" on Vimeo.  The thumbnails looked fine in the video blocks on SQSP.

Now trying to link these same videos to a video page (not just a block) on same SQSP site.  (Page is in draft form, so not yet published and visible on site.)  All prior thumbnails look blurry.  To try to resolve, created new thumbnails for videos as follows:  1.  Took screenshot from video and saved as .png file.  2.  Uploaded this file in Vimeo as new thumbnail and saved.   Then copied Vimeo link to revised video.  3.  Completely deleted earlier version of same video from SQSP video page, hit save and also refreshed page.  4.  Selected "Add Video" to the SQSP video page, copied the Vimeo link to video w/ new thumbnail and hit save.  The revised video and new thumbnail are now visible to me on the draft page, but the thumbnail is still blurry.

I need to have clear and crisp thumbnails wherever videos appear on the SQSP site.  Is this a problem with SQSP video pages (vs blocks)?  How can I resolve this issue?

Thank you.

kcln52