I have two PMUPs. One of them came with the ATK and I purchased a spare. I was away on a business trip and noticed that my tank wasn't topping off. I had my wife check the PMUP and she found that the pump was making noise, but not actually moving any water. I had her take the pump out of the water and put it back in and it started to move water. The next time the tank needed topping off, the same thing happened. I figured the pump just needed cleaning so when I got back, I put my spare PMUP online and it was working fine. I then gave the original PMUP a vinegar bath and set it aside. A few weeks later, we're in the same boat with the spare pump. This is extremely frustrating. I can't imagine I need to clean the pump weekly especially since it's sitting in a container full of clean RODI? What could the issue be?

Thanks,