Hidden Failure 

My Roland C380 pedalboard also developed a peculiar problem with some reed switches. They work on their own. However, if a neighboring chromatic pedal is pressed, they fail most of the time, preventing a heel-tip legato from being made between these pedals. The reed switches had no strange appearance. I ended up changing the defective pairs (the reed switch of the pedal that failed and the other one of the neighboring pedal), which solved the problem.

Submerge the faulty reed switches in water or alcohol. If the glass seals are breached you should see liquid ingress.

So have the same problem. Worked my way through ten reed switches, all failed after 5 minutes use. I fitted to model train to switch a micro led to simulate pantograph flash. But after a couple of circuits the reed switches fail. I can see a very small flash. So bought from different supplier, they are failing. Next step was to fit a capacitor, there visible some some micro flash on led. Or diode and treat reed like a relay coil. 3rd idea drive a transistor. But perhaps the soldering heat is causing the glass to unseal. I have soldered at the tip of wires. Perhaps i try next a screw block connector so no heat is involved or just wrap wire around with blob of super glue and on the glass bead ends. Otherwise stumped. Only switches used in past were epoxy sealed in a mounting block.

thank you very much for this insight. I have encountered this many time already. It puzzles me, now I think you are really getting on point on this, the oxidation may actually block the electronic connections even though the reeds are touching each other, nice work sir.

Very useful and insightful video. Thanks for taking the time.

Not unusual in my experience. Some minor oxidation of the contacts can cause eventual problems with this result; most electronics technicians with telecommunications experience learned about "wetting current" through contacts early on in their training. Although a reed relay is sealed, I don't think the relay is evacuated, so some air remains inside the glass tube. Decent design of the circuit should include some low current flow through the contacts to reduce the incidence of this type of failure.

A unique set up IE mounted over head Reed switches with blanking off metal plates

Good tips. I wish you had a video on how you wired that pedal board. I like the idea of making a circuit board.