There is usually a plastic ferrule that makes the transition from a tube batten to the rod batten. Check for a nail that goes straight through the tube batten and the ferrule, this needs to be removed first and then ferrule will usually come out with a bit of force.
Over the years I have had both glued and unglued. The glued ones used epoxy, so you could not soften it with a heat gun. You had to cut the tube just below the inside extent of the ferrule.
Most failures were split tube ends, such that the ferrule went up inside the tube, thus making the whole thing shorter. The solution has been an aluminum cover that fits over the outside of the tube end. Too bad they did not think of this 25 years ago.