have look x-carve friend what is wrong on the pics. can you see on the first projekt the line is clear and straight the others get like doubble why??? and only on one site, i think i lose steps maybe because when he is done with the job and goes back to 0 he is not right one the spot… hope you understand what is say 
I had similar troubles when I first set up my first machine. First - try tightening the GT2 pulley set screw. Next - check the tension on your belts next - and make sure the belt path is clear and free. Getting this tension is a bit tricky, but it has to be pretty tight. Finally - check the voltage setting on your controller and verify the wiring is completely ok. If your power settings are off, you could be introducing chatter into the system.
This may be backlash which is essentially what John is suggesting, something is loose. I had a couple experiences with this, either a loose wheel or, most recently, one of the set-screws fell out of one of the motor pulleys and that was loose. Check everything.