[UTM 9.4] AP30 Rev2 not working after UTM Upgrade 9.3 to 9.403-4

Hi guys,

I'm having one AP30 which is not working anymore after I upgraded our UTM from 9.3 to 9.403-4. 

I already recovered the AP several times now (https://www.sophos.com/en-us/support/knowledgebase/118843.aspx). After recovery the log says

TFTP: TFTP_WRQ opcode from 192.168.99.9:46759
Finished changing back the network interface settings
AP successfully recovered.

After restarting and connecting to the network again, the AP appears then in the Wireless Protection module. The UTM pushes the new firmware to the AP again.
Logfile says:

 2016:06:01-17:25:29 firewall awed[15479]: [A4000B62C898328] sent firmware /etc/wireless/firmware/AP30.uimage to device, releasing connection.

And thats it. This one AP then hangs, left and right led is blinking permanently. UTM says, this AP is inactive. Other APs working fine.
Any chances to get this AP running again?

Thanks,
Sven