Any idea how frequently the buttons themselves do fail?

I'm fairly confident that I've had one (the recirc button) go bad, as it would constantly hiss indicating a vacuum leak, regardless of whether in or out. (for a while, I could wedge the button to the side with a piece of paper folded up, and that halted the noise for quite a few months.) I don't believe it's the vacuum line from the button to the servo, as if I clamp that line a couple of inches behind the console, the hissing remains, and of course, if I clamp the vacuum source line, the hissing goes away.

There remains the possibility that the line to the servo is cracked right at the junction to the switch, however, I've looked at the line, and it seems ok. For now, I've simply blocked the vacuum line in front of the firewall. better than the incessant hisssss.

I've tried once to get the 3 button console unit out from the dash, however, my progress was stymied, I think by the metal bars to the side. I'll have to give it another whack, if I can find the unit somewheres.

just curious if anyone else has had the switch fail.
thanks,
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