ES-Timer Record failures?

[Tom81]

Sometimes my Panny Es-20 fails to timer record a program that has been properly set and the status reveals plenty of record time left on the DVD- Ram disc. I am talking mainstream network channels (not pay channels). Even the schedule menu confirms recording is possible.
This problem seems to appear when the Ram disc has been filled up, and random programs have been erased (defragmented disc?). If you are using a new disc or one that has been re-formatted it does not appear until you do some random erasures.
I am about to take to Panny service /technical support and was wondering if anyone has encountered the same problem?
I was wondering why there is no defragmentation availble for DVD discs.

[Tom81]

I want to explain further what I mean by randam erasures. You record a DVD-Ram with say 6 ep one hour programs and erase four them which should leave 4 hours. But in reality, you only cantimer record for about 1-2 hours. I also want to add that this same disc can be recorded for the full four hours left if you manually start recording.