Before you sling your problematic Panasonic in the bin, you may want to try cleaning the spindle. This has worked wonders for me on my current recorders: I have a 3 year old DMR-E55 recorder (a fantastic old machine which gets used to play & record EVERY day) and an LG GSA-4082B multidrive in the computer, but this method has also fixed many malfunctioning Playstation 2's, and DVD-ROMs, RAMs, CD drives, you name it.
The symptons of your Panasonic requiring a spindle clean are as follows. The machine may start to feel sluggish, particularly when formatting a DVD-RAM, performing erase functions, and may take longer to recognize discs. Then, you will start to get errors during recording and erasing, failed formatting, and the machine will not recognize some discs. Eventually it will be totally unpredictable and unreliable, and you may find that even after dismantling your machine and cleaning the lens most thoroughly, the problems persist. It may still play CDs and shop bought DVDs, those functions are the last to go. I will almost guarantee that this means a spindle clean is needed, although many would incorrectly blame these symptoms on a dirty lens, or even a defective laser, but the reality is, if the machine worked perfectly once, the laser is almost certainly fine. Panasonic use trusted circuitry to ensure a stable laser output.
The spindle is the little round platter inside your machine that your disc sits on. Discs go into the machine and there they are placed on the spindle, after which a circular magnetic grip clamps the disc into its final position, the disc being sandwiched firmly between the spindle and the grip. "Yeah, I know all this already" I can hear you shouting.
But the correct functioning of a spindle is absolutely CRITICAL in such a precise piece of technology as a DVD-RAM recorder, there is no room for error here as a dirty spindle will not spin the disc perfectly evenly - it can introduce wobble and jitter into the disc which even the cleanest lens will not cope with.
You do need to open up your machine to clean the spindle but it is well worth it if your machine is out of warranty. Take off the outer lid and locate the screws that hold the lid on the drive unit. There are usually four screws, two at either side. Remove those screws and that lid should now be loose, but don't use brute force - on my unit you have to jiggle the drive lid around a little towards the back of the unit. It will lift off.
You should now see the spindle. Notice the black rubber on the outer part of the spindle. With isopropyl alcohol and cotton buds, gently but thoroughly clean this rubber. It can sometimes look surprisingly dirty - carpet fibre, dust and tar from heavy smoking are the usual suspects in my experience. Clean the whole spindle too, then go back and clean that rubber again until it doesn't leave a mark on a fresh cotton bud dipped in alcohol. You may as well clean the lens while you are here. If you haven't cleaned a lens before, dip a fresh cotton bud in alcohol and brush the lens very gently with it, the lens will move slightly as it is spring mounted so don't be alarmed. Just be gentle. At this stage it's a good idea to clean the grip which is set into the lid of the drive unit. Now put your machine back together.
You should have a Panasonic that's as good as when you bought it. The first thing I would do is insert a DVD-RAM disc and format it. You should notice the speed difference, and of course, a successful format is a good sign in itself. My E55 first packed up 5 months after I bought it, and it didn't occur to me to clean the spindle even though I'd been fixing PS2's that way for a while. Well, it did, but it was under warranty and I got a replacement. That was nearly 3 years ago, and I have cleaned the spindle twice in that time, most recently yesterday, after a bit of erratic behaviour showed itself. But we are heavy smokers in this house - most people wouldn't need to clean it that often
Of course there are preventative measures you can take, like not putting in dusty or fingerprinted discs, cleaning the innermost part of discs you put in, and NOT handling a disc with its hole, just use the outside edge.
Anyway, I hope this helps somebody. The posts on CDFREAKS have been helpful to me for many years, so I hope I can put something back. It would be good if you could let me know if you fix your recorder using this method, and if you have any questions just let me know.