To me, it mostly appears okay from the outside. Or maybe the top of the left screw might be popping up a bit. I don't know what your best option might be. Contact Fostex or your audio store for a repair/replacement?
My left cup is a bit loose (but hasn't changed) and I haven't done anything about it. Probably over a year since I bought mine now though.
Edited by namaiki - 2/20/14 at 4:02am