I think @drwtsn32 has it, especially seeing that your original post says that you use OneDrive, which has somewhat different code (compared to some other destinations) and is using the Microsoft default timeout.
The short answer is probably the suggested one, but because you possibly are looking for the explanation:
suggests an oversize remote volume (dblock) size of 100 MB. Not normally a problem, but might timeout depending on Internet speed. Most people get this on uploads (many technologies are slower uploading), however you’ve uploaded about 84 GB yet are getting this timeout on test downloads after actual backup.
“RetryAttempts”: 4 may be the 5 total tries on dblock file, but About → Show log → Live → Retry can say.
You can probably also press the
Verify files button for the backup to look at its verification in isolation.
If you’ve been testing different remote volume sizes, it’s also possible you sampled a bigger one this time.
The default saved log shows the name of the test file that failed, and a fuller log (e.g. live) shows the size.