[sdiy] Advice on finding cold solders?

[Pete Hartman]

I have a VCO module I'm building that seems likely to have a cold
solder or solders on it.  If I twist the board (hold each end, rotate
hands in opposite directions) I can make it either work or not work,
at will.  This is a professionally made dual layer board, so it seems
unlikely that the problem is one of flaws in the board itself (though
of course I can't rule that out conclusively yet).

By "work" I mean "oscillate" :-)  I get output when I flex the board
one way, and it stops either when I stop flexing or, on the rare
occasions when I let go and it keeps going, it will stop if I flex it
the other way.

I have wiggled individual wires, and been unable to find one that was
the culprit.  The closest I came was pulling on a couple of the wires,
but in the end, that pulling appears to have been putting the same
twist on the board.  And it doesn't take much twist.  I'm not
deforming the board much at all when I flex it.

I have redone a small number of suspicious looking joints including a
couple that I'm pretty sure were cold solders (insulation in the joint
:( ) and I've reflowed a few others, but I still have the issue.

I'm at a point where the only thing I can think to do is redo ALL the
panel wiring (5 pots, 5 jacks, and a 3pdt switch) and/or reflow ALL
the joints.

But before resorting to that I figured I would call on the greater
experience pool out there, and ask if there's is some strategy for
finding the bad joint or joints that just isn't occurring to me.

Thanks

Pete