That's the solution, thanks.

All I'm doing is changing the image_xscale and image_yscale values before reloading. The duplicated objects appear behind the originals. If you reload more than once, the duplicated objects are moved correctly, but the original stays the same.

I have live_call() at the top of the Draw event with the code I'm changing. I have obj_gmlive in this room, and the GMLive server detects my game successfully. The error persists even if I add sprite_set_live() in this room's creation code.

Any idea what I could be missing?

Seconding that, primitives are enough to make a character model. Here's one I made using only primitives:

You could make hands with half-spheres for the palms and cylinders for the fingers, and you could use a cylinder for the neck. With that said, if you wanted to make something more complex, you would have to use something like Blender.