When you logout, I think laravel updates the remember_token field of your users table. If you have some kind of listeners on the saved event to deal with your id logic, you could try moving them to a created event instead and see if that fixes it.

Where would I check this? I don't have any event listeners that I am aware of. I did at one point which just logged the SQL queries but nothing else now.

Looking at your error stack, your user gets saved due to the remember_token and then firstOrCreate gets triggered. I'm not sure where you would have listeners set or what is going on with your code but you need to figure out why the firstOrCreate stuff is getting triggered on saves.

did you get any further with this?

Getting this error intermittently from mobile devices..