I had the same issue that KoKos noticed. If he hadn't posted about it here I probably would have left them running for a few days like that. I just remotely logged in to all of my rigs and noticed the invalid JSON notifications. Sadly, I don't have any logs nor do I know for sure when it occurred.
I can only add that it sucks :/
Im guessing you were both (and perhaps other users aswell) connected from before the most recent changes, since then Ive made no changes so it should be good going for now :/
If there is no more server stumbling blocks ahead, you and everyone else will regain the lost time in a few days, probably the best and only way to look at that.