Repetier Host and object placement

Morning allBit of a newbie question here.SystemMac Pro 5.1 running OS MojaveLatest Repetier that will run on my Mac 1.2.1(106)Slic3r as installed with Mac Repetier 1.3.1 devGeetech i3 C pro with Firmware I3proC_V1.0.05.hex from the Geetech siteWhen I import an STL in to Repeater, it sits square on the platform, nicely centered.Slicing tab then shows the item off to one side to the right.When printing , it sits almost correct on the bed, but not quite.Not sure where to start all bed settings seem correct, but I am guessing not.I did try a standalone Slic3r version 1.3.0 and that gives the same result.Any help on where to start appreciated.Even if I can go to a later firmware than the geetech firmware ..I see talk of Marlin firmware ..is there perhaps a later version that might be better?Sorry maybe very basic question, but my last printer was MakerBot with all bundled software and no need for this hassle...it just worked...Thank you