whoops, sorry, ive found the solution weeks ago! 
had to install this “flake”:
i say “flake”, cos they want you to use overlays, but since its cooler to use flakes (get it?) i went with the snow (get it? no? ok ill stop).
i ramble about my misadventures here…
never had an issue since with that custom kernel by valve…
edit: EXCEPT for the fact that it has NO cache for the kernel (last time i checked). yep. you will have to build a valve steam deck kernel on your own steam deck for 3-4 hours. on every update.