Sophos APX320X keeps restarting, cannot register in Sophos Central

Hello,

my APX320X keep rebooting, after start it is getting IP from DHCP (separate DHCP server controller )

After that I'm able to ping the AP IP for 20 seconds, Led status is blinking red

after that it goes unreachable and this scenario continue, Led status all 3 leds turn on for a few seconds

Tried to reset the AP (Hold 8 sec) and factory reset (20 sec) but same scenario, the AP keeps resetting.

In between AP and UTM, there is switch only, rule allows full internet access.

Product: SG 320 v9.706-9

I have a ticket open more than 1 month, they sent me a second hardware with the same fault.

Now I need the AP, but I have no answer from technical help desk in the last 7 days.

Kind regards