Well on the bright side, if they are inviting you back it means you aren't giving off bad cultural vibes.

My $0.02:

Try to press harder for feedback. I've generally had no difficulty extracting feedback on rejections, especially ones where I could be re-invited back ("well, without understanding what reasons I was passed on last time, it doesn't make much sense for either of us to invest in another round where the same issues may very well exist").

All else fails, consider mock interviews. There's paid services out there that will do this -- and you'll get detailed feedback.

Yeah - I am going to look into mock interview stuff more - hopefully something where it could be in person or at least on camera too. I'll press harder for feedback before accepting another interview loop. I tend to smash most phone interviews - so it's probably something special to the in-person aspect. A lot of my friends think people are writing non-technical things because there's something else more "problematic" for them to say that wouldn't fly in their write-up. Like - "he had rbf", "didn't laugh at my jokes", [insert unacceptable reason #48352], etc.