Aug 18th? Geez, I'm sorry about that. Most of the time when I mention that I was born in August I have to endure stories about how many dictators and mad-men were born the same month.
Anyway, I wouldn't think that op-amps would be the variable from input to input; I suppose it could be capacitors/resistors. More likely to be switches/bad contacts. Or even crap that humidity has bonded to the boards. Have you cleaned the strips? Find some black-market FREON and scrub or immerse as much as you can.