So, i had this issue and submitted a ticket. could not find legit answers anywhere so now that i have an answer, i will share it. When i was farming Vakkiz, i don’t know what i did that made this happen but yesterday afternoon, Tuesday, 5/29/19 Arizona time , not sure if that matters but, Vakkiz spawned in skeletal form.
According to the ticket i submitted Vakkiz does not drop anything when in skeletal form.
Now, today, i log in this morning and it spawns in skin normal form and drops the scale no problem. so, the only clue i got to this was when the GM said you have to kill it before it switches to skeletal form. assuming if it spawns in skeletal form then you have to wait for it to switch back before killing it? idk. hopefully this helps someone in the next many years to come!