I came across the same problem today (noticed i had repeaters with 1000s of rows) and stumbled upon this thread.
I created the following script to convert the data of a file field into a repeater. This worked when there was a file uploaded (field has data) and should be inserted into array of repeater on first position.
https://gist.github.com/slackday/947569a2adf7300e26027a920a20ede0
Use at your own risk! I’d advise to make database backup and test in local environment first.
