We have just released rest-server 0.11.0. It includes a fix for an issue where during transfer, a file could have been corrupted. The details are described in PR #142. The full changelog is included in the release.
I stumbled across a small problem, but it was easy to fix. Renamed the name of the user and the corresponding data directory. Thank you for rest-server 
Feb 11 18:17:26 server rest-server[3291660]: Ignoring invalid username "user_data" in htpasswd, consists of characters other than letters
Update: Reason for this problem is → https://github.com/restic/rest-server/issues/131
REST-server 0.12.0 is now out and it includes the fix for the underscore problem. Grab it here: Release v0.12.0 · restic/rest-server · GitHub