We seem to be getting random ones getting 400 error, ChromeOS flex and Chromebook proper, some work when restart, but otherwise, I've had to deprovision them factory reset and same model replacement. Then (after adding it the openest wifi) I do not enrol it and sign in with a work account and it updates, then I enrol it (it powerwashes) go through the normal enterprise enrolment and it seems fine.
I think its an Update with the Enterprise Admin Google side, but am not sure. Hmm we just had to sign in on the unfiltered wifi to get it to work the first time, seems alright after a reboot.