Hey @blakerobinson,
do you have that also on your phone and when playing via Chrome? Could be a TV issue though.
You could also try to reboot the Chromecast on your TV and see if that changes anything.
If nothing helps, I would recommend to contact Stadia support as they might have more troubleshooting steps that you can do in this case.
If you have HDR enabled, turn it off (you can do this in the "Display" section of the Stadia app). See if anything changes.
It's def not the TV. It's only a few months old and isn't used heavily. Also,h the artifact displays only on Stadia.
@blakerobinson is it only an issue in RDR2?