I've installed two T750SE AP's, one AP is configured correctly but the other one gets a102 error "configuration update failed" when moving this AP into a AP group and/or changing it's AP name.
The correct configured one is configured in the same AP group and they're both running the same firmware version 220.127.116.11.301 (also checked through SSH on the specific AP).
The faulty AP is and stays online in it's default state so it seems....
Somebody have any suggestions???
Try to factory reset this AP, delete its entry from controller and rejoin.
If still failing, try to fetch output of below command from AP CLI.
get syslog log
Check in log if you can find the reason for failure. If you are not sure what to look for, open up a support case for help.