I'm getting to the phase where Tsukuyomi turns the field into the moon, and we get the dark/light debuff stacks.

However, when I try to switch the debuff, it keeps the stack count while changing from dark to light, or light to dark. I observe the other players in the party getting 1 stack of the switched debuff. This is not happening to me. Is this a bug, or is there some small detail I'm missing for it to actually go down to 1?