Did you make a mark of the original adjustment so you could put it back? The nice thing about the V9s adjustment is that it is fairly precise in that it doesn't drift like some of the older models did. Putting it back may at least get you back to being able to read original discs.
so I adjusted the height of the laser rail
I have gone through several V9 units and the lasers on them seem to fail quick, even though the coils are not burned. Also for some reason on these models I have never had a pot adjustment that seemed to help much. It's as if the machine pushes it for all it's worth and then it just takes a dump.
Like Spedmetal said, most likely your laser is going south. I got a 400Q from richspsxparts.com and put it into one of my V9s and it works pretty good, but I don't know about backups. I have never copied a PS2 disc so I don't know how well it would do in that case, I usually copy all my games to the hard drive and run them from there. If I remember correctly though that unit did play a DVD movie that was on a DVD-R (single layer) so it might do OK.
EDIT: I just remembered that the azimuth adjustment can really goof things up if it has changed over time. I have seen a lot of units that over time the adjustment slug will back out about a quarter of a turn. You could try that after you put your sled height back. I would suspect that as being a problem before the sled height on a V9 because like I mentioned earlier the teeth on the adjustment wheels on these units have a little more bite to stay put than the older models.
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