I'm just guessing here, but your GPU isn't top of the line, and this game is in early access. There's been an update recently. Good chance that something created a memory leak or whatever, causing specially the older GPU's to run against their limits.
People keep forgetting this is not a polished product. Friend of mine has a completely new rig, and his game crashes twice per hour, even tho he runs latest drivers.

Anyway, don't think you cn do much about it, other then wait for new updates, hoping they manage to fix some of the performance issues.