In previous generation transmitter units, the vent slits are under the unit, and hot air does not easily escape, causing overheating and malfunction. I used cooling packs above and below a rather heated unit that was malfunctioning after being on for about an hour or more. In few minutes, the unit cooled down and regained proper operation. My long-term solution that has worked is turning the transmitting unit upside down;this helps dissipation of heat, which in turn prevents heat-related malfunction. Just to help further, I also installed a thermostatically controlled cooling fan right above the unit, although I don't think it was necessary.