I compared rings on both cups and it doesn't seem like it's broken. Maybe the ring is not holding the grill tight enough.
I'm definitely going to ask Hifiman and see what they have to say about it.
Mineral oil for the yoke swivel joints.
Also don't swivel free-handedly, firmly grip the extender piece of the yoke so that the torsion is put onto the swivel joint, not the headband connection piece.
I concur though that the logo pieces that secure the yokes to the headband are way too weak, it's a blunder on Hifiman's part. They are coming out with new planars next year though, so we might see a complete design change that fixes these things.
I just tried mineral oil and it definetly got better.
Too bad it's so difficult to untighten the screw because I'd really like to have them even more loose.
Good advice on how to swivel, I'm going to be very careful when swivel from now on.
Thank you both for your response.