My CNC router has CNC XPro V3 board, three limit switches, and GRBL Panel. I had to replace the limit switches because one of them was not working. Now, when I home the machine, I get Alarm 8. This didn't happen before changing limit switches. I have limit switches at the home position and not at other ends of axis's. Should $20 and $21 be set at 0? If I test the limit switches, the checkmarks stay on instead of going off. I test X-axis limit switch and the checkmark stay on. If I test Y-axis limit switch, the checkmark for X-Axis goes off and checkmark for Y-Axis goes on. If I test Z-axis limit switch, the checkmark for Y-Axis goes off and checkmark for Z-Axis goes on. How can I fix the problem?