The symptoms of this problem are that the antenna can be extended to its full extent but it cannot be pulled back and the external sheath seems to move the antenna easily by hand.
One of the causes therefore that has been found was that the blocker on the far end of the internal piston had been broken off by mistake such that the piston could be removed entirely and the blocker would remain inside the metal antenna casing.
It seems that the piston with the copper coil thread wrapped around it is not separate from the blocker such that the easiest fix is to simply use some glue, such as JB weld, to glue the piston to the blocker. Some caution has to be taken to remember to slide the piston inside the metal cylinder first because the metal cylinder cannot be removed after gluing the two parts together.
On closer inspection, it can be observed that the two parts have broken off, due to a jagged edge on top of the blocker that gives it away. Interestingly, the two parts are not threaded, and it just seems that they were glued together.
JB weld is not a destructive glue like superglue, seems to be organic and forms a tight bond if left to cure properly. The metal cylinder caddy should be kept from falling onto the blocker while the glue is curing and can be attached to the piston with some sellotape temporarily till the two parts bond.
The result is that the antenna should now not be moveable by hand and only the motor should be capable of extending or retracting the antenna.
KB5WIA claims that they experienced some fluttering during transmission and the issue was traced down to the ATAS antenna where the lower screws holding the motor circuit together with the rest of the antenna had rusted slightly and started to make a poor contact between the body of the base and the antenna pole.
So, so the fix seems to have been to chip the paint around the holes made for the screws and to use metal washers instead of nylon on the screws, which should result in a much better contact between the base of the antenna and the antenna shaft.
A little bit of non-corrosive vaseline has been added to the screws after the modification in order to make sure that the humidity does not make the antenna rust.