I will do the file uploads within the next 6 hours. Some further data:
- if I repeat the operation, starting with a fresh copy of the original file, all extracted portions act the same way.
- I uploaded the large original file to Vimeo, and it displays fine, with no black out at the beginning.
- I don't have a project file. I do simple editing manually by marking sections then marking them for deletion, and then saving the result.
- I've done this successfully many times in the past. The Zoom meeting and recording was initiated by someone else this time, and the resolution was different: 2048 x 1152 vs the 1920 x 1080 I normally work with.
- I did comparisons of the various parameters for old, and problematic recordings, using a couple of utilities, and the only difference I could find is the resolution, and some parameters I think are related to that, like average bit rate, etc.
Thank you for investigating this issue, as I suspect it may reoccur for me in the future.