So I changed the assert to an early exit, which will skip updating the rendering for mobs on frames that have NaN transforms, but shouldn’t crash anymore. If it was a precision issue on the client side, it should sort itself out quickly and shouldn’t have any noticeable adverse effects in the game (i.e. might skip updating an entity for a frame or two).
TLDR: This should be fixed on the latest build on Steam. Thanks for the report @MichaelD7 & for the help @max99x