If the delay is controlled by a blinker bulb, then it might have shorted out or someone didn’t install a 455. Just a guess.

Dave

I’d plug that bulb into a playfield or backbox socket and see if it ever blinks. Seems odd to have a bunch that don’t blink. I have found some that blink on or off at weird rates so that they don’t look good in the back box and then I swap them out. Sometime old ones are better, other times I prefer brand new ones.

The delay circuit is counting on the current draw to be low enough that the light stays on so you hear the buzzer, but not forever, so that when the bulb heats up and blinks, it lets the relay drop.