We just got back from a week plus and our pump did the same thing- at very low flow rates (barely turned faucet on), and it ran continuously when open further.
When trying to conserve battery and reduce all sound, constantly on and off does not meet our goal. Great flow, though.
We'll be adding an accumulator and replacing some hard lines with flexible and insulating some vibration points.
In our experience, an accumulator is good for a few flushes as well when the pump is off. Imagine coming back from being out all day and having the pump off while you're gone, and sneaking into the bathroom and either having to go switch on the water to flush, or if just washing hands, walking through camper with soapy hands, LOL.
Well worth it, IMHO ;)