efnfast- Well, it *does* sound a little weird and I can't say I've ever noticed either of mine doing that
The one head is *not* reversing direction in the sense of it's elliptical path, that I'm sure of but note that the "randomness of the "random orbital" action comes from the heads being able to spin in either direction while being driven along their elliptical path by the motor; one half of the dual-action is motor-driven and the other half is free-spinning.
If you can live without the thing for a while, I'd send it to the guys at Cyclotoolmakers and have them check it out. They're good and honest, and they won't do unnecessary work just to get some of your money. Or at least give 'em a call and talk it over...again, they're nice, helpful folks. Link:
Cyclo Toolmakers