I’m certainly no expert having just recently completed the build of my X-Carve but I had the exact same problem except it happened on the first attempt. The Z-Axis went to the top and it just kept running like you had happen with your second homing sequence. In my case, I had a bad GShield and got a new one, then it worked fine. Then it happened again. I had the V-Wheels too tight, binding the carriage before hitting the homing switch. I loosened up the eccentric nuts just a hair and then it worked and it’s not been a problem since (I did end up using loctite to prevent the nuts from tightening or loosening). Check your V-Wheels and take a Multi-meter and make sure you have voltage to the homing switch. If you have no voltage, it could be a bad solder, a bad connection with the plug that goes on the GShield, or the wires. If it isn’t any of those things, then someone with more knowledge and experience may be able to solve your problem. Good Luck!