How old is the DVD reader/recorder? Have you ever cleaned the laser and the reading device with a cleaning disc?
I returned and exchanged this particular model more than four times as I recall. At one point, I was told to keep the last of the broken machines because of the many problems. I have one that plays but doesn’t record, and one that is very tempermental. An example on the latter, I taped something from the TV without a problem. Hours later, I placed a pre-recorded disc (movie) and it failed to read. Sometimes it reads a blank DVD and at other times, it doesn’t.