Well this was a frustrating one. After many months of smooth running, our S5 started failing the auto bed levelling before even making the first contact point, and it would fail consistently after that showing the error message "Difference between detected height of both PrintCores exceeds realistic values". Replaced print cores, cleaned the bed, rebooted and rebooted, then after a while I discovered the connection to the sensor inside the fan bracket has sheared. This seems like a huge weak point considering how often the fan bracket is opened and closed. So just a heads up really!