Are you using radius for the authentication?
AVP = Attribute Value Pairs
If you are using radius for authentication (MAC auth or 802.1X) and wrong attribute are sent by radius, you may see these error. I am not 100% sure but this should be the case.
Also double check the radius configuration on controller and on server side.
So you are seeing those errors on Unleashed event logs or specific AP support logs?
Syamantak Omer | Community moderator | Sr.Staff TSE | CWNA | CCNA | RASZA | RICXI