Polymost: Voxels that have the cstat flip bit set are rendered incorrectly
The problem can be seen on money and letter sprites when turned to voxels, here is an example:
This only occurs in Polymost, in Classic the voxel is rendered correctly. It appears as if, after the process of converting the voxel to a 3D model, each of these planes has its texture flipped independently, rather than as one complete unit, resulting in the disjointed effect you see in the first image.
Note that cstat flip bit support for voxels was introduced in commit a1eb1829.
To reproduce this, I unfortunately only have the money voxel. The effect is more subtle, but you can still recognize it if you compare between Classic and Polymost. If you need the mail voxel, please contact the author Dzierzan.
To reproduce, simply extract the package and run
eduke32.exe -mh voxelmoney.def