Please explain how to remove the magnetic disc from the tail cap without damaging the threads in the tail cap.
It appears to me that the tail cap spring is on top of the magnet and both are held in place by what looks like an initially undersized (smaller than the threads) conical washer which was then press fitted into the tail cap by being expanded during assembly and is now non-removable.
Here is a picture of the tail cap from this review of the FC11:
https://budgetlightforum.com/t/-/60423
NOTE: I do not have a Wurkkos FC11 to personally examine (and did not purchase one because of the magnet), but do have two Sofirn SP40 headlamps (that came with magnets even though I purchased the older ones that explicitly stated they did not have magnets) which use the same tail cap design and I would like to remove the magnets from those because they cause my compass to read incorrectly.