Brand new out of the box CSX B23-7/B30-7 diesel locomotive and the couplers on the front and rear of unit seem to be slightly low of any rolling stock I try to couple it to.  Result is that unit will not stay coupled.  All the rest of my rolling stock and locos match up perfectly.  The coupler unit is mounted to the shell and I don't see any way of adjusting or changing the coupler  height. 
I just can't believe a QC problem of this nature.   Is there something I'm missing?

Is there a DCC decoder that can be wired into Prairie loco/tender #51562? will it work with any command unit?