So I've been enjoying Stadia very much since launch and since launch things have been working pretty much flawlessly for me. Using a hardwired Chromecast I was able to play in highest quality on my 4K TV. Stadia would constantly report excellent connection. However, since a couple of days performance has been degraded for me unfortunately. I am now stuck at "good" connection quality and I only ever get the 1080p stream. I also seem to be getting artefacts and the stream changing resolution occasionally. However, I can't reach excellent quality anymore and it bothers me a lot, taking all the fun out of Stadia.

I have checked everything I could form my side. The Router has been reset multiple times and it is ok. Stadia Speed Test reports the same speeds as it always did. There are no new network devices and monitoring the bandwidth usage on my router, I don't see anything interfering. There have also reset the Chromecast to no avail. There is really nothing else I can do about this except contacting my ISP, although this would probably be pointless, since I can't report anything being wrong with my connection except for Stadia. Very frustrating.
@GraceFromGoogle Is there anything Google is doing from their end on Stadia infrastructure in Germany currently? Are there any other issues which might affect performance in my location at the moment? How can I go about this issue? We really need more detailed diagnostics when looking into such problems because as things stand now my ISP and Google support will probably send me running in circles.