A couple of months ago I saw this for one particular client. I was not certain if I had done too many for this client within a window of time. It was like that for days. Then they all became unblocked.
I am not certain if it is a matter of rotation or the client having a hold placed on the board. But that seems odd because I see shops there one day, gone for a few, then return. So why would it be locked if they could just remove it for a few days anyway?