On my W126 their is an adjustment for the parking brake which is just a mini drum brake system. The shoes or whats left of them may have worn a lip in the rotor and could be holding it a bit. So turn the star adjustment in reverse to pull them in.
Than get a torch out and torch the rotor hat, than smack with hammer. A little heat will pop it free.
If you plan on reusing the rotor, use a block of wood or rubber hammer.
