I finally found the cause of instability in my network: seems that you cannot mix V1 and V2 in one network.
Found multiple people also have this issue.
Note that i tried a possible combinations of locations etc. All the time conclusion is: as soon as you remove V2 from the network (all other devices V1), all is super stable.
As soon as you add a V2 device, network becomes unstable.
Is there is solution in the works ? Note that nowehere it is mentioned you cannot mix multiple hardware versions. Which means that people might be buying deco's that are not fully compatible with their current setup.