Can't say it exactly, but since the FAW cable is in use, there's no flaw to it.
Maybe my right ear had more wax in it, I don't know for sure. ^^
But after my measurements, my little OCD was triggered almost all the time.
So it has to be the cables fault, you all know what I mean.
I never compared the cables after that, which is a bad move by myself, I've to admit.
If my time will let me, i'll give it a "second" try, but then the FAW is starring at me asking
WHY?
Maybe you're first move should be to clean the sockets on the headphone, and the plugs of the cable, with some alcohol/ipa to make sure there's no dust/waste, which may cause a bad connection.
What I figured out in a short test today is, that the plugs of the OEM cable caused some drop outs on the left side, but a small twist sort the issue.
No issues with the plugs of the FAW cable so far.
At least I can say that after 4 years of ownership, despite having a ZMF VO at hand, the Era-1 is still my favorite headphone for metal.