Tried a heat gun on a stubborn helicoid, ended up melting the grease seal

Working on a 70s Pentax Spotmatic last weekend in my basement. The focusing helicoid was completely stuck, like someone glued it with old dried grease. I figured a quick pass with a heat gun would loosen things up. Big mistake. The heat softened the seal ring right at the edge and it sagged, now the helicoid turns smooth but there's a permanent wavy spot. I've done the solvent soak and freeze method before, that worked fine. Should have just been patient. Has anyone else wrecked a part trying to speed things up with heat? How do you get stubborn helicoids out without damaging nearby plastic or seals?

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