Sometimes the knob of the F1 device becomes unresponsive or fails to reset properly when pressed down. You may follow the instructions below to troubleshoot.
Remove the knob.
Loosen the rod.
Refer to this video for details.
If the knob can not be removed, please pry it out carefully as is shown in the following way.
If the knob happens to break, kindly reach out to the xTool customer support team for a replacement.