Cloud Alpha right side louder than the left?

Previously used the OG Cloud, bought the Cloud Alpha and It's got a noticeable loudness imbalance, the right side is louder than the left. Tried with or without the extender, different sound outputs / devices, it still persists. I'd try a different audio cable but I can't find any that would fit in the earcup (it's got a weird port that needs a slimmer jack). Slightly tweaking balance in Windows helps, but I can't easily tweak it on my phone f.e.

Is it a faulty cable problem? Any suggestions?