In my previous, previous life, I was flying a non glass, 737 300, to somewhere in Spain. I can’t remember where. However we were cleared for a NDB approach. Light cloud at 2000, about 4 Oktas. When we got station passage, the FO, who was flying, started the correct let down procedure. Looking out the window, and also the the DME, something suddenly did not add up. I told him to stop the decent. We actually got “station passage” about ( from what I could work out), about 5 nm South of the NDB. I have never figured out why. But it gave me a BIG SCARE.
Having read above, maybe it was night effect. I know it was scary. It was only the fact it was almost CAVOK, and I had been there many times at night, and it did not look right, triggered me.