I set the automatic file transfer update interval to 60 minutes, but files are only transferred once per day.

The automatic file transfer update interval is the interval at which the DX, MV, or other unit's recorded data files are checked. If the check finds that there are no un-sent recorded data files, none are transferred. If recorded data file creation on the DX, MV, or other unit is 1 day, file transfer will also take place once per day.