I made a change to the endcaps to solve this problem once and for all. I drilled 3 holes in the side of the cap, making sure not to drill too deep and ending up in the inner cavity. Then I cut some thread in the hole (M6) and put a very short bolt with a hex head in the hole using 3M 5200.
Now I have three points on the cap I put the blade of a screwdriver to and gently tap the cap from the tube.
What Desalator should have done is make the cap diameter lager then the tube diameter so you can develop some grip on the cap. Also the price is insane.
I'm a bit underwhelmed with the way this watermaker is designed, although the dual voltage thing is very clever. The control logic is well below par for the price I would say.