Permanently sealed Grover tuners....

Currently doing a tuneup on a nice 12-yr-old Gibson Hummingbird... setting the action, new strings, oil the fretboard, polish the frets, etc.

One of the Grover tuners is really tight, regardless of how much tension is (or isn't) on the knob screw. These are supposedly "sealed-for-life" units and also, supposedly, need no lubrication.

The knob screw is a phillips head, which I've heard that indicates the tuner was made in Asia, as opposed to the slothead which means made in the U.S.

At any rate, has anyone got an idea for loosening-up a tight sealed Grover? Or maybe just chalk it up to a defective tuner and replace it?