Oh no! Plucking is such a complex issue. Has your vet done thorough exam and blood work to look for causes? Once you rule out underlying medical issues, we look at behavioral. How long has he been plucking? Typically, the longer it goes on, the harder it is to break the habit. So many possible reasons. Diet, boredom, stress, the list goes on. Here's a thread that might be of some help. https://www.parrotforums.com/threads/plucking-a-search-for-answers.52217/
It's a place to start. I've been there. It's heartbreaking to see our feathered friends pluck.
you are not alone, many of us have pluckers...its complex, a definitely difficult to impossible to stop if it's been going on on a while...sometimes after everything has been tried you have to just accept and love them they like they are.
I'm going through the same thing. I'm so sorry! my heart breaks for you, and your ekkie. There really can be medical issues contributing. I adopted an ekkie, and brought him to the vet the first week I had him. Who referred me to a avian vet who is amazing with my ekkie. I found out that my ekkie had medical issues going on contributing to his feather plucking. I would always recommend taking any parrot to the vet whos feather plucking to do a process of elimination. Avian vets are very hard to find. I know mine does online counseltations. I hope more vets can go to this because us parrot owners have to rely on one another in situations that are not ideal. Not to mention that different parrots have different needs which makes things even more difficult.