I have been experiencing strange WiFi behavior since yesterday and I have now done some experiments to nail down the problem.
I have two WiFis, 1x 5ghz and 1x 2.4ghz. All devices use the 5ghz, only my printer relies on the 2.4ghz.
I updated last weekend and have had no problems until yesterday - at some point I was not able to visit the embedded web server (EWS) of my printer anymore. I experienced weird behavior in LuCI to, I often had to press menu items twice on my phone. At night, things then became even worse, I could not reset my router to 'vanilla 18.06' anymore.
So I flashed the sysupgrade image from 18.06, which worked fine.
Now the observation: if I start from a fresh image and activate my 2.4 GHz network only, I can reach my printer. If I put it to a cable, I can reach it too.
If I connect to the 5ghz network with any other device and start browsing the internet, the 2.4 GHz connection becomes "crippled". There is no indication of this, the speeds still show 30-72MB but I simply can't reach the printer and it does not get properly discovered from my laptop (the CUPS webinterface at one point found it but only after several tries). From time to time the printer spits out pages which were tried to be printed several hours ago. If I connect to that 2.4ghz network with my laptop and try to access LuCI, I experience a very slow build up of the interface, so the speeds must be very slow.
I have no idea what this could be. Any ideas? Is there a bug in the driver?
It's not formally solved yet - I updated this morning over my breakfast coffee (6am in Germany ) so I want to see whether it's actually changed and the problem is gone.
I'll mark it as solved then of course once I'm confident that this solved the issue actually.
EDIT: So far no outages and I can't indicate anything pointing towards a not-solved. Thus solved. Thanks for the nice support, that was really frustrating