Because I don't have the time to define hundreds of dummy sprites for all frames of animation I only really make ones for the first frame of spawn/ready. This causes no issues in hardware, but on software renderers, it won't draw at all and flood the console with "R_DrawPSprite: invalid sprite frame" errors.
I isolated part of my mod into this minimal example here.
Seems like renderer bails out immediately before checking if a model is being used.