If you have problems with your prints in the center of the plate, it may be because the arm (Y-axis) is not calibrated correctly. You can check this by starting a calibration of the Y-axis under "printer tools" in the app. Follow the instructions in the app. Note that it is important that you use a very accurate measuring tool, such as a caliper, to measure the length of the printed Y-test. Then enter the length of the Y-test in the app to complete the calibration of your printer's Y-axis.