(23 Dec 2021, 12:12 am)N391OTY wrote 6177, 6179 and 6182 all appear to have entered service Wednesday 22nd at Chester-le-Street, while 6180 has returned to Washington. (All taken from bustimes, not my own observations).

More surprisingly, has 5236 really returned to service at Riverside ?

Without a doubt a ticket machine error. I believe the driver training vehicles aren't legally PCVs anymore so they can't be used in service (not 100% sure)