IIRC Ademco was once a large supplier of glass reeds?
I have experienced both Knight & CQR to fail, open, closed or spaz out....
I think graded contacts with pcb's are worse than resistors fitted into BS contacts for failing
back in the golden age of DP when Arf was getting on the waiting list for a bus pass...
You could measure the circuit during servicing & find failing contacts which going hi Ω, an extra 50Ω ain't never going show up on EOL