I have an LD-002R that has been working fine until just now. When it tries to home at the beginning of a print the Z-axis motor continues to push the buildplate down on the screen and won't stop. It does the same thing when I attempt to home the buildplate as well. Luckily I caught it and prevented it from cracking the screen. I have just now updated the firmware and the problem hasn't changed. Does anyone know what the problem may be?