About 2 weeks ago I started having some problems with a Martin Mac 550 and an Elation Power Spot 575 switching and flashing when connected to DMX. Both fixtures work fine in test mode. I have tried pulling the fixtures down and connecting them directly to the console, even tried different addresses and consoles. The problem remained. They went down within a day of each other. What would cause this? The problem seems to be with the fixtures themselves.