I have this issue with one MSC. The only time I've ever gotten a rating at all is when I cancelled a shop (with plenty of notice, but I got dinged) and when I had a shop that the client questioned (it was accepted, but I got a mediocre rating). I've done numerous shops for this company since, with great feedback from the editor. But no grades. So my rating in the system isn't what it should be. But it doesn't stop me from getting shops, so I'm OK with that....
I learn something new every day, but not everyday!
I've learned to never trust spell-check or my phone's auto-fill feature.