What happened?
On the CORE One equipped with the INDX, the offset of the tools compared to the first is calibrated through the Tool Offset Calibration. If the offset of one of the tools deviates too far from the expected range, the printer will show the following message: "XY tool offset calibration failed. Make sure the nozzle is clean. Be careful it may be hot."
Error name: Tool offset out of bounds
Error code: #36130 (CORE One INDX)
How to fix it?
Filament unload
Make sure that the filament is unloaded before the calibration process.
Nozzle cleaning
Use a small brass brush to clear away any old plastic stuck on the nozzle. Avoid contact of the brush with the hotend cables, as this could cause a short circuit.
Tool offset calibration
Go to the printer menu in Control -> Calibrations & Tests -> 12. Tool offsets calibration, and redo the calibration.
Reduce vibrations
Any form of vibration propagated to the surface under the printer, or a not fully stable surface under the printer, might cause a false reading on the loadcell, causing the homing error to trigger.
For example, a printer that is in operation next to your printer can cause vibrations that are propagated to it, potentially causing a tool offset calibration fail. In that case, stop any printers next to the CORE One with INDX, and reattempt the calibration.
A possible solution to dampening the noise and vibration of a printer is to add some additional padding underneath the printer.