I did the FFC patch in July 2023 and haven't done any FW updates since. Today I went from .100 to .600 FW and the FCC patch still works.
I did what others have said:
1) Downloaded & reinstalled the patch (patch applied successfully)
2) Updated DJIRC from .100 to .600 FW.
3) Reinstalled the patch but had the error about waiting.
4) Updated the
M3P whilst waiting.
5) Waited about three hours and reinstalled the patch (patch applied successfully)
6) Check radio and it is in FCC mode (the line below the 1km is about 5mm lower than when in CE mode)
So anyone with concerns, just do as I did above. Worked a charm.