I have had the same problem. It can be traced to a loose connection with the cable. With mine it was the JR adapter cable. Send the cable back to Ikarus to be repaired. You will probably have to have the diode for the trainer port replaced on your transmitter as well. I have two 8103 transmitters ....when I started having the problem I tried the other transmitter. Unfortunately the loose connection fried the trainer diodes in both of them.