I decided to reset mij zigbee network. After that, I added all 4 routers first, and end devices later.
The good news?
In developers I see all devices and the routers are ‘routing’.
The bad news?
I had hope that resetting zigbee would finally solve the cpu overloading (often >200% and losing wifi connection to Homey). That is still happening
I have contacted Athom support and they are looking into this case. Hope to hear more on Monday.
I came across an interesting article why our zigbee network seems to go crazy after the 5.0.0 update. It’s due to a change in the network key that was in the current Zigbee devices. Hope this is useful for those interested.