Vintage Synth Repair

I initially was just doing my repair on the left panel ribbons which
went successfully though much worse than usual.  The right panel had
worked perfect always.  But after finishing..I discovered that the
thing has a quacking sound when keys are hit occasionally *and* that
there is a single voice that always is different...but it doesn't
follow the analog channel.  Anyway not to elaborate on that mess....

It got worse.  Suddenly..none of the right panel switches work.  I'm
not kidding.  This is absolutely bizarre.  I tested them. No contact.
 I short across and can actuate the functions that correlate to the
switch I'm trying to test for continuity.  There is no reading on my
diode checker and they don't work.  They are all open. There is no
disconnection in EITHER cABLE all the way down to the main body of the
plastic.  Has anyone..ever seen anything like this?  (I know..I'm the
only one on earth who's ever seen this..again.  right? I mean it
doesn't even seem possible.  That that many switches
just..simultaneously corroded.  Man..my breath must be HORRIBLE! 
Seriously... does anyone have any right panels left?  The left usually
fails so I'll bet someone has a glut of them somewhere.  -Bob

Ok, I somehow got bad reading on the channel non-correlation of the
missing vco.  Really baffled as to how.  I evaluated the schematics
thinking maybe there was something along the way that if a data line
was clamped somewhere it might cause that effect...but convinced
myself there wasn't some dual dynamic overlap thing going on, checked
again and found that it was the suspected thought that a solder blob
had gotten under something.  So now it play all vco's.

However it still quacks intermittently.  The quack is as someone
reminded me a warning buzz that can be turned down.  However it'd be
nice to figure out what's wrong there...and the BIG CLUE...is...there
is one button switch (yes which I'm having to manually do) which will
cause a quack every time.  PItch pedal!  Yup.  You hit it, you get a
quack.  Every time.  

And yes..I still need a membrane panel. I should look to see how hard
it would be to do a manufacturing run of those.  But if anyone at all
knows a source please let me know. Otherwise it'll be midi patch
changes for a while I guess...-Bob