Duh... forgot to mention that vWLAN is on 2.9.0.HA.
Hmm... I may have 'jumped the gun on this'. After I posted this, I tried the firmware update process again, and now it's stable. Moderator: This post can be deleted, sorry for the trouble.
No problem. I was going to offer that currently if major versions are mismatched (i.e. 2.9.X needs 2.9.X code) then you can run into reboot problems such as this as the configuration may not push to the APs correctly. It's a common problem.
Glad everything is working!
ADTRAN Product Support Engineer