after going line by line over the switch config I found the culprit.
On the client access stack the following parameter was set
vlan dot1q tag native
removing the line and everything started to work.
Anyway I think Native Vlan Tagging is quite useful on client access switches.
The following port configuration on the stack was also working but not stable, after some time packes where dropped so it is no solution.
! not stable workaround for WAP if param. "vlan dot1q tag native" is set on the stack interface GigabitEthernet1/0/39 switchport access vlan 1616 switchport trunk encapsulation dot1q switchport trunk native vlan 999 switchport trunk allowed vlan 1616-1630
Is there a possible working solution with "Native Vlan Tagging" and Wireless ?