If the system still has a good refrigerant charge, then it is probably not the compressor seal. If it does not and you do indeed replace the seal, the MB manuals indicate that the seal should be replaced on the bench. I don't think you can fit a puller in place without removing the compressor.

An overcharge causing this seems to be unlikely.

With the clutch clean, I think I'd run it a little and see what happens.

Good luck,