prusa i3 pro b help

Hello, I have a prusa i3 pro B and when I print something it will start, then at a random layer in the print (sometimes first layer sometimes half way through it seems random) it stops for about three seconds and then it starts printing again in another location as if nothing had happened so I end up with models that are offset by as much as 3 inches or as little as 1/16 inches. I've tried greasing the guide rods and threaded rods, swapping the places of the motor drivers, printing from SD and USB independently, pointing an air hose at the drivers to cool them, twisting the wires to limit electromagnetic noise, and adjusting the pots. on the drivers and on the power supply. After all this it still changes nothing. PLEASE HELP ME. I am so frustrated and lost!