Geeetech

Sometimes my z axis motors spin in opposite directions other times they do not. I checked the wiring and it is correct. I am using ramps 1.4 and arduino on the GEEETech prusa i3. It is almost as if when they receive resistance they reverse directions. Please help

1)if the wires are correct conect,it can't be working like this,please give me some more details .
2)tell me exactly your I3 type,I'll sent you the corresponding firmware,so you can try to reburn your firmware to fix this problem.