3 axis router will not zero after moving cnc...

This is my second cnc router that I have made. The old cnc run great until the computer burn up and so I decided to build this one seeing how I had to get a new computer anyway. I can zero out this machine and run a file or just jog around the table and hit (go to zero ) button and it will not go back to the zero I had to start with. I have the motor tuning correct and I have run the steps per program in the mach3 and it is correct. I am running Keling Tech 425 motors and my driver board is a Toshiba TG6560 . I am not sure if the driver boar is cheap or not but the motors and driver board are brand new. I am losing steps or something crazy is going on that I dont not understand. It seems to be going negative past the zero that I had set before the movement started. The Z works correctly It is on a 1/2" acme lead screw. The Y and X are running a belt. The motor gear is 10 tooth and the gear on the opposite end is a 15 tooth gear. I have it setup for 100 steps per. I checked it with mach3 and it is correct. I am not sure what is going on but when I jog around the table or run a file it will not go back to the original zero. Any help would be great before I take a torch and hammer to this machine..lol Thanks in advance Jeff