Hi David, Thanks for answering. The operation mode is "Wi-Fi Router". This was the setup before the firmware upgrade. I have tried 2 switches, both are TPlink unmanaged gigabit, models are TL-SG1005D Ver5.0 and TL-SG108E Version 6.0 If i remove the ethernet backhaul, the deco's work fine by conencting through wifi. I tried bypassing the ethernet switches by connecting 2 deco's directly with a patch cable, but the slave deco starts going into a loop of green and then red lights. I have started the downgrade and will try using the ethernet connections and test. Thanks for the link.

  @Neil_f 

 

I found the issue. One of the main deco's ethernet port is faulty and is not working. Swapping the unit with another one and making it the master solved the problem.

 

Now the next task to get technical support to replace or fix the faulty unit.