Symptoms: gears were slipping bad. Applying pressure to the pedals were causing them to slip hard... I almost fell on my ass trying to accelerate from a stop light. Not safe. I almost lost my faith in chainless bicycles today... until I got it fixed and took it for a test ride.
Fix: first off I tightened up the shifter cable and checked that the marks on the rear hub lined up in 4th gear. That helped a bit. I took it for a spin and it still slipped hard while applying pressure. Damn it! So I removed the right side crank arm / pedal and noticed that the face plate on the front hub / front part of the shaft drive was very loose and some grease was leaking out... fail. I tightened that up by fitting two allen wrenches in the holes on opposite sides and turning hard. There are about 6 holes all around. Now I took it for another test ride and everything felt much more efficient with no slipping. I've been missing out. I wonder how long that piece has been loose and slowly getting looser. Anyway I hope there is no permanent damage and plan on adding more bearing grease soon. Ordering it now. Also adjusted disk breaks.