Has this happened since your LED in the transmitter got broken? If so, chances are that it is causing a short that is loading down the 2012D transformer. It has a thermal cutout in it that will disconnect the power until the transformer cools off. At first it is four minutes, but repeated attempts will shorten this time frame.
I think that once you get the LED replaced, the problem will go away. If you are not able to get it repaired, just clip away the remnants of the broken LED so that the wired connections to the LED are no longer touching and you should be fine. You just won't have an in-use light. Don't do this while it is plugged in. Also, don't do this until you find out if you can get the LED replaced.
