I monkeyed around with my trunk handle for about a week trying to solve this same problem without any degree of success. I gave it up as a bad job and ordered a new repro handle for $40 from Mike’s, which for all outward appearances matched my nonfunctional, unrepairable one (which may or may not be an original - I can’t tell).
Anyway, the new repro not surprisingly required some cutting, filing, and careful fitting of the main shaft, which took about an hour. When all done, it looks good and works fine and I can lock my trunk again. My coupe (my avatar) is not restored for judging, it’s restored for functional and safe use, so the repro part works for me.