Unable to flash previously cross-flashed LG drive (BP50NB40 -> BP60NB10)

I have an LG BP50NB40 that I flashed to BP60NB10 using the instructions in the forums back in January. I'd like to change it to BU40N, but all of my attempts have produced nothing. I'm fumbling through the long forum thread [here](https://forum.makemkv.com/forum/viewtopic.php?p=135752&sid=4bf70d9c3fd460e43775a247ffbd5c98#p135752) trying to reproduce what others have tried when taking a previously-flashed drive from BP60NB10 -> BU40N, using the flasher's Recovery feature, but nothing happens at all.

No matter what I try to use as the recovery firmware or the new target firmware, when I do a power cycle and then load MakeMKV, it still says my drive is BP60NB10. I'm honestly surprised it's not bricked at this point.

Has anyone else run into this and figured out what to do for this to work?