Reply to Headphone/Cueing Problem

Hi there, I am wondering if anybody knows the solution to my problem. On my Kontrol S4 when I plug in headphones to the socket on the front for cueing, sound only comes out of one side of the headphones. In the settings I have it set on the output monitors to both left and right for each side but it does not seem to work.

This is using a stereo headphone plug and then plugging any set of speakers/headphones in. When using a mono plug the signal is split between both sides of the headphone.

Thanks!