I'm aware this will be fixed with the arrival of the new battle UI, but until then, I'd suggest banning this combo. The reason behind this lies in Prankster not working correctly in PRO, which results in it being broken. To be more specific, dark types are not immune to it (which isn't a dealbreaker as that was a case in Generation VI), but it lets certain mons (most notably Klefki) freely defoging opponent's hazards away (obvously even on dark types), while preserving your own screens, which wasn't a thing existing in Generation VI as during that time Klefki couldn't learn Defog. Considering that Klefki is mostly used on hyper offense teams which usually include Dragonite and mons equipped with sash, it is definitely a thing worth considering. Furthermore, there are already certain combos that are being banned in this game because of them not working like they are supposed to (for instance, sash + memento or wonder guard + sash) so I don't see a reason why this shouldn't be the case too. To conclude this, I'll once more emphasize, I just want the combo of Prankster + Defog to be banned until working properly, not to ban Pranskter, Klefki or anything else.