When I reopen the survey from the Sent Box (on ipad, v 3.5.164), I can see all 11 sample records in the repeat. But, only the first 4 samples collected actually made it through to the related table in SDE.
I have only one potential clue, but it's probably a long shot. The "Sample Notes" field in the 5th record contains gibberish (butt dial maybe??). Could that have somehow prevented this record, and the following 6, from being sent through to the database?
I haven't yet tried to resend the survey.