good point! Thank you.

I would like to add that the catch mechanism might need some lubrication. Friction might be  holding the bonnet pin for a while.

Dan, Thanks for the advice. I looked at it again, before seeing your reply. I noticed the moving tang on the latch was untouched. So the 'pointed post' on the bonnet is not touching that moving piece as it comes down. So I moved the latch to the right (as looking at the engine bay) by about an 1/8th of an inch. One drive and the hood stayed the whole time. I'm not calling it victory yet. But looking good. Henry

The "pointed rod" as you call it is adjustable. You need to loosen its lock nut and extend it so it does fully catch in the latch. The latch mechanism should also be centred under the pointed rod. In your case the latch position should be OK as it is partially latching.

Ideally the latch should grip with the bonnet just barely kissing the rubber rattle bumpers at its corners. You should be able to push down on the bonnet a little against the spring around the pointed rod. In other words, the spring should be holding the bonnet up and the bonnet itself should not be sprung at all.

It's a 1969 Mark II Traveller with the release knob through the grille.  Closes solidly but wants to release after only a few miles.  Yes, prefers to pop open on a bump/dip in the road.  I'm sure the pointed rod is fully engaging the catch, because I can't simply lift the hood without sliding the release arm.  So I'm guessing I need to move the catch left or right ever so slightly?

Henry