Delta printer layer shifting

I have built my first ever 3d delta printer and facing layer shifting problems.The layer shift is rather inconsistent, it occurs during some prints at irregular heights and mostly towards Y-Z axis. I have all pulleys tightened, belt tensioned, stepper current adjusted. While layer shifting steppers drivers are warm but not too hot plus i have a cooling fan for them. I am driving printer with ramps 1.4 and heated bed with 17 amps power supply. Software version Marlin 1.1.6 and simplify3d/cura for slicing. I tried reducing printer speed and acceleration, changed drivers but failed to resolve the problem. Please help me this is my highschool project and need to get it working. I have posted photos with failed prints and succesful prints.

Edited 1 time(s). Last edit at 03/10/2018 10:59AM by kirito22091996.

Do you see binding on one of the carriers? Are the smooth rods parallel? Does the nozzle scratch when it moves across the part? ( overextrusion building up )

The carriers are smooth did not feel any bindings. The parts are cnc machined and rods are parallel too. I use z lift for retraction and mostly print one object at a time so nozzle scratch must not be a problem.Do you think 8 bit controller might be the problem?

Edited 1 time(s). Last edit at 03/13/2018 03:20AM by kirito22091996.

Do you have any lateral play in your rod-end bearings? If you do, you could try adding springs between the ends of each pair of rods to minimize that.

Also, any play between the hot-end and the effector?