The same issue on an M1 and on a sling box 500 so I don't think it's the model.
My connections says the RELAY Diagnostic screen that you get by pushing the three bars button for a few seconds.
Bandwidth is about 3.5 Mb per second
But I am only getting 640x480 resolution in the highest quality mode.
Do I Need to reconfigure my router so that I get TCP and instead of Relay and how do I do that ?