Panasonic SC-AK27 stereo system loose memory & malfuction

I have stored 12 radio stations in memory and after working on the radio for 3 to 6 hours, the light on the CD (I have not inserted a CD), as well as on the TAPE, CD and TUNER stops and starts flashing. At the same time, the radio stations are lost from the memory! I have to turn it off, turn it on again, set the clock and store the radio stations in the memory again. How can I repair this defect?I have stored 12 radio stations in memory and after working on the radio for 3 to 6 hours, the light on the CD (I have not inserted a CD), as well as on the TAPE, CD and TUNER stops and starts flashing. At the same time, the radio stations are lost from the memory! I have to turn it off, turn it on again, set the clock and store the radio stations in the memory again. How can I repair this defect?