It sounds like what ever you are using as the triggering device has some slider/control/parameter that is the culprit.Look in BOTH manuals for whatever control is used for pitch bend,and explore that.Might try Yamaha's website for links to older gear;their tech dept has been pretty good.Maybe shoot them an e-mail.
If that doesn't work,barring anything amiss in the DX,UNPLUG BOTH,re-initialize;then hook back up and see.