Stremio can barely play 720p stream on Apple TV

Streamio (and Plex) are both struggling to play any videos over 720p, and sometimes can't even do that. Stremio works fine when I play it on my phone or my laptop.
Yes, I have a debrid service. Yes, the internet to my Apple TV is fast enough for 4k. Yes, I am playing videos labelled RD+.

I am at a total loss as to how to troubleshoot this.