I agree with the above analysis. Clean it, lube it, put it back together and see how it runs. Don't over do it with the oil and grease. Grease on the gear teeth, oil on the pivot points. Use just enough to keep things moving smoothly. Too much turns it into a dirt collector. Do pay attention to the rollers. A small drop of light oil at the pin is good. Use a needle oiler if you have one. If the problem persists, then we need to look at the E-unit. With any luck at all, that won't be necessary.