Can you elaborate what do you mean by "broken"?

I have HE400se, it's been a roller coaster experience in the first week I was using it. It sounds distorted in the low end and sounds like broken headphones in several songs even in relatively low volume. Even I had a little imbalance. BUT I decided to give it some time, andd it's getting better and better in sound quality (not the tuning wise because that could be my brain just adapted to its sound. But I like the tuning since the first time I was using it nonetheless). I don't know why but the distorted sound and imbalance isssue has been gone completely. I didn't really trust the burn-in methods in headphones but it seems it's more impactful in planar headphones (yeah HE400se is my first planar).

My point is, if your 'sounds broken' experience is similar to me (and you have returned the unit), maybe you just didn't give it more time to it. But if your experience is completely different, I'd like to know more! Thanks.