have you looked at the switch itself?
i had an s14 kouki power folding switch that i traded for an s14 zenki power folding switch.
when i got the zenki one, the opening function worked perfectly.
but the closing function didnt work at all.
i checked the mirror motors, and worked perfectly fine.
so, i took the switch apart.
turned out that the "fillament" under the motherboard had burned, so it wasnt passing the signal.
so i just soldered some fillament lines, and it worked better than new.
so yeah, just a thought
p.s.
does the mirror work perfectly the first time around? but heats up and stops working after a while?
cuz i mean, its not like youre gonna be foldind and unfolding them like 20 times straight.
in the vid, the first time it worked pretty good.
maybe thats what happened to the seller...he only tried them once and saw that they worked.