So, I changed Ross' promotion classes to myrmidon and archer
myrmidon and archer can not equip an ax.
To Promotion to a class that has weapons that they can not equip,
it is necessary to turn off weapons from the Promotion screen.
There should be a patch made by the author of girls.
and , I ported it to FE8U.
It might be solved with this patch.
NAME.en=Display/Hide Weapon On Promote
However, since you do not attach reproducible data, there is no guarantee that this can be solved.