I had the same problem with one of my l2m's. If I ran it at a relatively low level, the tweeter would stop working. If I turned if off and back on, it would come on and then drop out again. If I drove it really hard, it would sometimes come back on. Took it to a service center where they replaced the tweeter under warranty. 3 months later and it's doing the same thing. Makes me think it's something other than the tweeter because it sounds fine when it's working. I think it's something in the amp or crossover really but I can't prove it.