Annoying as speed tests showed a good connection on the wire. Once it was removed though, stadia went from poor connectivity to excellent.
I was playing Stadia fine for months and one day couldn't get over 1080p and kept getting disconnect warnings.
I was using the CCU wireless and a the Nest router is about 5 feet away.
Did a test and connection to the router was capping at 30mbps. Not sure what was going in but a router reboot saw it go back up to a connection speed of 150mbps and I was back at 4K.
So everybody should always keep that in mind too