Reply to Two problems with my 2 months old S4

Hey! I recently got back a brand new Kontrol S4, since my last one had the volume faders problem. They sent me a replacement unit. However, now it seems like the 1st Effect panel button (FX1) to the left is broken. It does not respond to every press I make all of a sudden. Sometimes when I press it, it lights up and then lights off in a matter of second. Very strange since it's such a new maschine.

The other problem is (probably a setting) that my output volume through the headphones (HDJ 2000) is pretty low. I can easily listen to max volume without feeling too much through my ears. What can that be?

Thanks in advance

Jack H