Since day one assembly and start up I have had intermittent gantry issues. Specifically the left Z axes (poop side) does not move with the right side. First I was told to check all wire connections. That helped for a while. The printer worked fine until the left side began to act up again while printing causing failures at different times during a print. Service told me to update firmware, clean and lube lead rod and remove any debris from the lead rod area. After finding no obstructions, cleaning and lubricating the rods it did not help. After unplugging and letting the printer sit for an hour, I restarted the printer and did a self check. The gantry on the right side rose and the left side followed with much growling and was 1/2 to 3/4 inch lower than the right. Again service said Check for debris, lube and update. This went on for two days. Now I have mentioned warranty replacement and have heard nothing back.
When I got mine, lead screw was totally unscrew with the coupler, check it