[namibj]

I'm pretty sure the RF seal of a microwave oven door is a resonance seal that doesn't depend on conductive contacts for the shielding effect.

If the door mechanically seals properly like it's supposed to, all should be fine. If the mechanics make it not be as flush as it used to, get rid of it or measure the RF power at it's operating frequency near it while it's running, to check whether it still properly seals the RF.