In the code, farrier is misspelled as ferrier so not all of the options are shown, and the flag is not cleared properly.
I amazed how this was the only bug report on this..and of course not fixed since Conclave got released.
Just like the far older culture modifier bug for joining holy orders, joing the opposite cultured orders more likely and others,
but i digress..
anyway, so..
in
ze_adolescence_events.txt
this is set
set_character_flag = ZE_13610_farrier
set_character_flag = ZE_13610_farrier_male
and this is how most options are triggered and how the flag supposed to be cleared
clr_character_flag = ZE_13610_ferrier
clr_character_flag = ZE_13610_ferrier_male
An e for an a.
There is no ZE_13610_ferrier flag ever set, so it's not a mix up of different flags.
Notepad++ search tells more.
Just posting this in late 2020 in the hope that maybe one day there might be a bug fix patch.