I have two floodlights on opposite ends of my home, controlled by one switch in the middle of my home. Initially, I tried wiring motion sensors on both ends of the home. Only one of the units would work at a time, the other would stay on. After installation, I read the warning against installing 2 motion lights on one switch. I decided to dedicate one of the floods to stay on all of the time and put the old flood fixture back up, and put one of the two motion sensors on the other flood at the opposite end. The motion sensor fixture worked about 5 cycles, then just stayed on all the time. I tried resetting at the breaker, resetting at the switch, etc to get it to work properly, but no luck. I assumed I must have a faulty motion sensor so I replaced it with the second sensor, which was a different brand. The second sensor worked perfectly for about 3 days and now, it has begun to behave just like the first one. It stays on all the time and can't be re-set to work correctly by turning off at the switch or the breaker. What could be causing this behavior?