For my two penn'orth... yes, as has just been said the problem lies with the metal tube and it's right angled bend. The cable jams because it wears a channel in the tube interior as it travels around the internal bend. This can be enough to jam the cable itself or cause the cable to fray and then jam in the tube. Over the years I have found that the reason for this is that the two rear bonnet style closers were not adjusted correctly... yes from the factory too! If you find your release lever is not functioning smoothly, you're yanking at it then it's out of adjustment. Rarely is it the cable length that needs tweaking, rather it's the latches themselves. It's just a case of using a flat head screwdriver to loosen them. Start with three half turns anticlockwise then close the rear of the hood down. When closed look at the seal under the hood to the body work... is the level of seal compression or the gaps the same both sides? If not adjust the cones until they are equal. You should find if the cable tube is undamaged that the hood releases easily whilst doing this. Once you are happy you can now slowly start to tighten the cones until you are happy that you have achieved an adequate seal and that the release catch works easily. If your tube and cable are damaged beyond repair It's best to not try and replace everything as you can really cause some damage here. Instead you can modify the cable length adjusting mechanism to hold the latches permanently open and as Dave of Monty fame has said fit hood latches inside the car. They look original and won't jam. Triumph Herold or Vitesse soft top versions are available and look very period. However it goes you can pat yourself on the back whilst drinking your well earned cuppa and treat you and the other half to a meal out on the money you have saved!
NB.
For those with a spare wheel if you just cannot release the rear of the hood then you can access the cones when the wheel is removed loosen them and hopefully you will regain control of the release lever, even loosening one often works or try getting two people to evenly apply downward force each side of the hood Frame. Best of Luck to those in this predicament and to all others ... just set your hood locks now to prevent excessive wear and eventual failure!
