There could be two different issues with them. As I understand it, some of the initial batch had a bad bushing that allowed the prop to spin backwards and they offer a fix for that. The second is sone of them over time can crack the little protrusion off that is inside the front cover or housing and has a little rubber bumper stop on it that forces them to go in one direction only. If the front cover or grille has what looks life a few fins missing and yoy do not have a stub with a rubber piece on it inside the cover that could be the other issue that takes a new front grille. I never had the first problem but did have the second problem after about a year of usage on a RKL controller set to switch from one the the other every 30 seconds. The ysaw a ton of stops and starts before this happened so I am still thrilled with the quality and Hydor took care of the issue quickly as soon as I notified them, the package was in my mail in less than a week.
