Have you measured the voltage on this? If it gets hot it means it is being triggered, that is it has a voltage on it which is too high. Could be a wrong part.
Back in the 60s on courses for teaching people to mend TV sets, part of the practical exam involved replacing components with incorrectly marked components, maybe yours are too. I would temporarily remove the diode by cutting the track, it can always be bridged back in circuit later.