Hey David,
As stated before, your portfolio is really strong. And you have also demonstrated tenacity in the way you have continuously polished it.
That being said, I think there are still details that can be tightened up.
What you are experiencing is very frustrating.
I know, as I have had almost a year of travels across Europe and to both US coasts and then crickets.
All of a sudden however, the most amazing opportunity opened up and kick started my career.
Obviously it’s hard to make any comments or assumptions as to how you carry yourself in interviews but you seem self aware and contemplative so if there would be anything that might trigger a negative impression, I would believe that you can identify and correct this.
You ask if another internship is the answer. That of course depends on the situation but for me, this was definitely the right decision.
Though the trainee position in SF was much more of a jr designer role than a classic internship, with a clear goal to convert to fulltime and a salary that reflected this.
Are you only answering postings or are you also cold calling firms and studios?
So there isn’t much more advice I could give then to keep at it and not give up.