Ultimately, I cannot tell you for sure whether I am 'interpersonally off' (whatever that may mean), but again, I felt very good about the interviews itself. I was engaged, asked questions, and never felt 'awkward' and I don't think I left people feeling that way.
During my master's program, I worked with a professor who had very clinical research interests, so as part of that I lead a weekly group. I got positive feedback from both my prof (who is a clinical psychologist) as well as the people attending the group. Moreover, I got positive feedback from my current mentor about being very personal when interacting with our study participants.
And then: Why would people email my mentor and tell him they were very impressed by me when, in fact, they just thought I was really awkward?
Yes, three times is a lot...