by Ken Task.
'...until the restoring procedure starts'
That's when max packets would come into play.
So, again, web server error logs? MySQL has gone away?
Query for DB settings for max allowed packets is?
In moodledata/temp/backup/ there should be folders with long names ... inspect one of them. One of the very last things done ... clean up of that directory - erasing contents then directory but only after restore has completed successfully. Ownerships/permissions?
Task or cron job task for cleaning up temp areas romping on a restore process?
Are locks being cleared?
Turn on debug!???
'SoS', Ken