My customer pointed me to another thing that has changed.
Because of the new feature application visibility the OUI resolution (ID the vendor of the WLAN adapter) was replaced with the more accurate information that was collected via packet inspection.
The thing is that AP37xx doesn't support application visibility so the field is "unknown" - could we get back the OUI ID for the "old" APs to get at least a idea what device vendor is connected to the AP.
MU1&4 are connected to a AP38xx and show the device type information
MU2&3 are connected to a AP37xx and show unknown