I’ve uploaded a small update for Savanna Sam. It mostly consists of a new setting in the options menu: "precompile shaders"

After loading a level, but before actually starting it, the game usually tries to precompile all shaders that will be needed in this level. This prevents the shaders being compiled on the fly during gameplay, which might cause stutters.

For most people, this option should just stay activated. However, on some machines, this process can cause glitches.

If after starting the level, you are suddenly flying through bizarre geometry and black boxes, then please restart the game, and turn off the “precompile shaders” option shown above before starting any levels. That should fix the issue.