It could be the headphone adapter. I know with my sony earphones, if I use the wrong adapter/jack, it sums to the middle and is no longer in stereo. Try a different jack but also make sure your routing in your daw is configured properly. Also, the saffire has its own routing matrix/configuration screen (seperate from the daw) so make sure you check it and make corrections if need be.
No problem on helping you out, fam.