Looking into this! I moved the likes system back to MySQL today which I imagine might be the issue :)

Yup, that's what the problem was, some of them didn't get brought over in the transfer back from Mongo to MySQL in preparing for the move on Friday morning.

Unfortunately, the reasons for the quick move from Mongo and the general method that mongo uses to store data resulted in the data not being backed up before moving, but we're left with the "insert" notification which means I should be able to piece it back together.

Otherwise, I'll use that to figure out roughly how many are missing and just award everyone those likes back up to where they were. I obviously don't want anyone to feel like they've lost / missed out on these :(