Creality Ender 5 Pro -weird Z axis problem

[3Dray]

Hi, I recently picked up a Creality Ender 5 Pro. The guy that sold it to me has done a 32 bit board upgrade, but never managed to get firmware loaded onto it. I fixed that easily enough (currently running hte Ender-5 Pro- Marlin2.0.1 - V1.2.1 - Endstop - Filament - TMC2225.bin) After playing around a bit with temps and such, I managed to get the thing leveled and printing. I downloaded and installed Creality Slicer, which I assumed would be the easiest software to start with. When I print a calibration cube, however, it does not look right. (See attachment) It seems the Z axis print exacltly twice as thick/high as it should. The 20x20x20 cube comes out 20x20x40.....? Any idea what I am doing wrong here? Probably a rookie mistake, but I can't seem to find anyone describing the same problem.