but Arthur, Rafaelo and Bandit are still missing the heart icon 
The above was written before what i'm writting now, I had the idea after writing all this to battle one of them and see if it fix the heart thing, I went to Golden Sand and got to battle Bandit, then I went back to his shop and the heart was there
I'm guessing the update need the player to "refresh" the affinity gauge by battling them once to get a bit of affinity point and understand that they're already full ? Posting this so people who come to read this later might have a clue if they got the same issue as me after the update
Edit : I totally forgot about the dicktionnary when I had the idea, but I just tried and renting a room to battle them anytime works too