Pioneer DVD-RW DVR-105 stopped working on MDD

I have a [url=https://www.applefritter.com/content/deep-space-nineterok-nor]MDD[/url] that is generally in good health. The major problem I have with it right now is that the DVD drive has decided to stop working. When I run OS X.4.11 or 9.2.2, the drive is recognized and spins the disc but fails to properly read the disc and ultimately ejects it after about 80 seconds of trying. When I try to boot from the drive itself, the same issue happens and it reverts to the what ever the default boot is set to (X v. 9). I have tried a variety of discs to include known good bootable Apple OEM discs which had been known to boot this machine in the past. What can I do to verify that the hardware has begun to fail? As the system's firmware was not altered and the systems does attempt to boot from the disc I am inclined to suspect a hardware issue but... How can I rule out that the problem is not a software issue? The drive worked before I installed 9 but it had been a very long period of time since I used the drive and cannot verify that this is the cause especially since the only changes I made were to add OS 9, not alter the X system folder or any firmware changes. While you are pondering this question (thank you, by the way), I wish to add a second DVD drive and am looking for known high performers. Since I may need to end up buying two, which models have worked best for you? I see good things about NEC drives but am truthfully ignorant in this area. I have great access to a local electronics market with tons of stuff I can browse in addition to looking for 'like-new' products on the web. If someone can shove me in the right direction, I would be grateful. TIA