Sequential circuits samplers

Greetings,

I just acquired a Prophet 2000 in decent shape.  The previous owner 
tells me he had it for ten years, eight of which the p2k was in 
storage.  He says the OS is 4.2. The memory has not be expanded at 
all (but that doesn't matter to me). I cleaned out the insides which 
weren't too bad, and replaced what appears to be missing mounting 
studs underneath the left and right extremes of the keyboard assembly.

The drive looks like it was replaced because there's about a half 
inch gap above the drive between it and the case.  I didn't remove it 
to get a closer look because it works now and I didn't want to upset 
it!  The previous owner doesn't know the history of the drive accept 
that it was like that when he acquired it.

It appears relatively clean overall; the thru/out switch was frozen 
so I put some contact cleaner to it and was able to switch it the 
thru.  The overlay looks very clean and the buttons and knobs respond 
well.

The original manual came with it in its original binder along with 
three disks.  They're old, but two of the three work, however the one 
I wanted to work has errors!  That would be the one with the piano 
patches.  I believe I've read here or elsewhere that I can use dd/dd 
disks, but I'd like to have that confirmed if someone is willing to 
here.

Anyway, the internal sounds don't seem right to me.  About 4 or 5 of 
the twelve make a sound when selected, the rest are fundamentally 
silent.  Does this sound like there's an issue?

When I was fooling around with the sounds I could load from the 
disks, it seemed that some had been messed with as if the mappings 
were off.  Not all of the sounds, just some.  Some of them did not 
play in the top octave of the keyboard, and one the lower octave.  Is 
this ringing any bells?  Any problems of note here, other than my 
unfamiliarity with the board itself?

Can anyone perhaps give me some things to look out for technically or 
otherwise based on what I've written here?

I used to have an Ensoniq Mirage back in the day, and have always 
wanted a p2k.  Now that I have one, I'd like to make sure I have it 
for a while.

Thanks!
Rich