Clefable Unite Move Buffer Bug

Recently I noticed that sometimes when activating Clefable's Unite Move automatically buffers the next input, even when I deliberately only press it once. This means that moves like Hydro Pump and Close Combat come out immediately as soon as it selects them, which is annoying, but the worst one is Block which is completely useless because the second input just cancels it instantly. So it's an entirely wasted Unite move since the wall appears for a second and cancels immediately without doing anything.

I don't know what triggers it because sometimes it works normally, but ever since I noticed it I started being very careful about only pressing the input once, and it still buffers the next input automatically over half the time.