The XL tool heads are connected to a metal profile on the back extrusion of the XL. During the selftest of the multi-tool head, the wizard will guide you through the Dock position calibration to properly align the tool heads. In case the tools are not aligned correctly, this error will be shown.
Error name: Dock position out of bounds
Error code: #17102
First, make sure that the metal profile that holds the extruders is all the way to the left side of the printer facing it from the back.
After that, restart the Dock Position calibration by going to LCD menu -> Control -> Calibrations & Tests -> 4 Dock Position Calibration. Align the tool heads again.