Aruba AP sending too large frames / Excessive giant packets

When a new Aruba AP is connecting to a Aruba controller, it is member of the default AP Group. For some reason the MTU size  in de default AP Group (and all new AP Group that you add) is larger then 1500 (regardsless the info that I found on AirHeads). This results in error messages on your switch:  FFI: port x-Excessive undersized/giant packets. See help.

To fix this you can change the MTU size for all AP Groups to 1500.

GUI:
go to Configuration - Wireless - AP Configuration
select the desired AP Group
go to AP - AP system
in the Basic tab enter 1500 in the SAP MTU field

PS. Alternatively you can enable jumbo frames on your switch.