Laravel Homestead-based Nginx/PHP returns 500 or otherwise times out after several hours of working correctly

Hi all. I'm encountering an extremely frustrating problem running the homestead base box of 6.1.0 on Virtualbox 5.2.12 — in short, after several hours of a working php/laravel environment on the Homestead VM, I'll start getting timeouts and 500 errors when I try to access my application. I can still remotely login to the MySQL database over port 33060 (default), but nginx/php is just not responding — and I'd like to figure out why. What steps should I take to resolve this?

The only workaround I've found so far is to do a complete vagrant destroy --force and rebuild the VM, which takes upwards of 20 minutes and is not a livable solution.

Will happily provide more information as necessary.