Battery, ear-cushion and inner foam-screen guides cover different wear points. The foam screens have separate left and right OEM part numbers.
What to check before buying
Cushions and foam
iFixit documents both the outer ear cushions and the inner foam screens. It cites separate Sony foam-screen numbers for left and right, so worn foam can be addressed without treating it as a speaker-driver fault.
Battery service
The battery replacement guide calls for fresh adhesive during reassembly. A used XM3 with reduced runtime needs a different job from worn cushions, even though both involve the ear cups.