Maybe this is a generic browser issue and cannot be fixed. 'On save complete' triggers even when a game is not saved, because of insufficient disk space. This is unfortunate and can cause great player wrath, because they will still get 'Game saved' notifications.
I remember experiencing it myself once, but can't remember if it was in Chrome or Firefox. I've had 2 players reporting it, who both solved the problem, by freeing up diskspace.