Another in-depth problem description did I add in this thread:
It was brought to my attention that it might be a good idea to share it on this thread.
In the meantime I discovered that when you opt to have a lan domain value configere in foris for your local machines it sets the dynamic lease boolean value in /etc/config/resolver in the common section to true causing all kinds of problems as the python script which is called when this value is set is badly broken.
And I also have this problem in foris that it shows 2 x fail for dnscheck although ATM dns is working (let’s see for how long though).