Worst thing about all this is that I very much like how these sound... I felt more boxed in using Hifiman HE600, and those were open, for crying out loud :< even compared to AKG K1000, Core doesn't feel like a closed pair of cans.
Bass is about perfect in terms of amount, and I can't complain about its quality.
Midrange is great, with forward vocals having proper timbre, exactly how I like it.
Treble isn't piercing at all despite being nice and clear.
Comfort is a cherry on top, no complaints there either.
All in all, I hope these QC issues can be definitively resolved.