Everest sliding patio doors

[Mr-H]

We have a set of these between the lounge and conservatory so they are sheltered from the weather. However, they are quite old, and there is what sounds like a flat spot on one of the rollers in the door bottom runner. It makes a gnarling and groaning sound most of the time. On other occasiona the door runs and sounds as sweet as a bell. I have been on to Everest - they say these doors are too old and they do not manufacture them any more, and I have spoken to a local Double Glazing repairer who says that Everest would never supply him with any spares anyway. I wondered if any of the brilliant ABs had any ideas?

[The Builder]

It could just be that the door has dropped. There should be (but don't bank on it) a small hole (maybe covered) near the bottom on the meeting face where you can get a screwdriver(prob. crosshead) in to raise the door to clear the runner.
If not, lift the door out and have a look. Might be fixable with parts from something else.