Chromecast with Google TV and LG CX 24hz not staying

[Colty]

I don't like motion interpolation and 24p with BFI on the CX looks perfect for a cinema effect. Motion isn't as smooth as my old Plasma, but this is very close and looks more like a theater projector.

The issue is that when I set my Chromecast to be 4k/24Hz, it defaults back to 4k60 (or sometimes even 1080/60) every so often. Sometimes once or twice a day, sometimes every few days. I know an Nvidia shield would fix this, but I'd really like for it to also do 4k/25Hz for PAL content. Plex in the Chromecast doesn't automatically switch the refresh rate even with settings on to do so. I'm fine with manually changing it when I occasionally watch 25hz content.

So what I'm trying to figure out... Is there a way to fix it randomly switching back to 60fps? And certainly avoid it switching to 1080p.