How do I stop desktop resolution settings in Ubuntu 24.04 VM from getting reset?

I'm running Ubuntu 24.04 (ARM) using Parallels on a Mac Studio. Parallels and the Ubuntu VM are all up to date.
I run the resolution of the VM at 1920 x 1200. Parallels regularly resets this to 1024 x 768, or changes so that the VM looks like it's zoomed out to 50% (some Retina thing)?
When I change the resolution (in the VM) back to 1920 x 1200, it all fine. But it's very annoying.
It's been going on for months, so it's not specific to an update.
How can I get Parallels to leave it at 1920 x 1200 and not zoom out (or use Retina mode)?