Given your past experience and high quality work, I’m wondering if what’s letting you down is how you present yourself during interviews (rather than what you present). It’s unfortunate because we can’t really critique it over the boards.
However… One of the most valuable things my university offered me was the opportunity to mock interviews with HR managers and Project Leaders from real firms, where they’d give you really frank advice immediately after, or even during the interview - I found out a whole heap of things I was doing wrong that I’d never have picked otherwise.
In Australia at least, there’s several firms that offer a similar service (for a small fee of course), and I can’t imagine it’d be different in other countries. While you might have trouble finding a firm that specifically covers ID interviews, getting good critique might be really valuable.