This kind of sounds like whatever was on the tip had oxidized severely over the intervening 40 years. So when you applied heat it couldn’t conduct very well, so it got hotter and hotter until it had an uncontrolled thermal expansion. This just comes down to especially with older equipment, making sure the device is clean, and if you apply heat be careful especially on the first startup.
This kind of sounds like whatever was on the tip had oxidized severely over the intervening 40 years. So when you applied heat it couldn’t conduct very well, so it got hotter and hotter until it had an uncontrolled thermal expansion. This just comes down to especially with older equipment, making sure the device is clean, and if you apply heat be careful especially on the first startup.