After doing some research, I came to a conclusion, on how to resolve a lasting spritesheet issue, where the Lamb's mask is facing in the opposite direction, when they're in West/East rotation.
If the uncompiled sprites are available, it's a matter of flipping this singular sprite, and readjusting it in Spriter.
If these are not at hand, it gets a bit harsher, since you need to re-create the Spriter project from scratch, using the sprites cropped from the sheets one-by-one, then let the game compile it, or look deeper in the Mod Tools for a workaround (which might not actually be there).