Cube rotations, and possibly face rotations are handled improperly when the model is spawned with a pitch and yaw of 0 0. Here is 2 demo models with their rotations set to 0:

and here is the same models with them set to 0.01, 0.01:

Unfortunately, I dont have a single nice line change that fixes this, mostly because I am too tired to throw one together, but a hacky workaround is to turn 0 rotations into very small ones, and that should work for most models.
BBModels are in a repo I made a minute ago for testing.