No solution yet. I trashed preferences, but that didn’t work. You’re the first post and it’s been 7 months! If it were a common problem, I would have expected more responses.
You describe exactly what I experience. It’s as if the color picker is color blind. I am not able to discern a logic to it in terms of the relationship between the selected color and the copied color – it seems random.
Maybe migrating to FCP X is the solution.