I need to update the above trouble with my findings today as it is appropriate to do so.
I have an musicstreamer active that plays without any interruptions, so i did not suspect any wifi trouble. But i totally forgot that any player for music and video will buffer its data to overcome interruptions.
But the Airgradient is sensitive to wifi trouble as it seems, so therefor generating errors…
Today i checked if there where some updates done in the unifi system, and see there, the 26th of aug it was updated, at that moment i checked other iot devices and saw very bad signal strength on 2.4ghz devices.
Well the conclusion is that the device is ok, but i find the different errors it is producing confusing.
I have to give Achim credits, he was right with his comment that it should be local connection trouble.
In this case my apologies for taking time recources.