Installed a new XF250 (controller and two gyres) in a new tank about a month ago. Noticed last week that one of the two units isn't spinning. When first powered up, the controller applies power to both units, but senses the one isn't spinning and stops after about 10 seconds. I switched pump plugs on the controller and the problem switched sides, so I'm fairly certain it's not the controller. There are no snails in the tank yet and the pump spins freely by hand. I dissembled and cleaned the pump and it didn't make any difference. I don't know what to try next.