Potential bug with 400% Rare Boost in AC Shop?

Of course it is hard to verify this as a user, but I finally gave in a purchased a 400% eare booster due to it lasting for 6 hours while farming Super Hard Advanced Quests. Started after Quna concert.

Ever since I used it my drops have been significantly worse to the point that I think I got roughly 1 12* and maybe 5 10*s through 2 whole cycles of Super Hard quests. The drops in the UQ that followed the concert also seemed horrible, and we also triggered the 300% rare boost from the jack in the box on top of it.

I will also be submitting it as a ticket so they can check the modifiers on their end, but I definitely haven't had this few 10* drops ever playing Super Hard advanced Quests, especially on +50 risk. (Of course I also didn't get any 13*s or Saiki, but that's not quantifiably the boosters fault).

Anyone else have any anecdotal experiences with the AC Rare?

EDIT: Just to add to the circumstances, I overwrite a 250% Booster with it.

iirc, some drops are fixed / scripted. I know in the "Bonus Quest" type quests that use the silver/gold tickets... the rare boosts don't work. (Source: +350% Rare boost total (with +250% Boost, and triboosts) that I used on JP version.)

@coldreactive that would suck if that were the case with SHAQs, but I haven't heard of it applying to them before.

@John-Paul-RAGE It seems that you can calculate the exact effect of rare drop boosters by comparing the growth of items gauge of collection sheets. Is there any English documentation about that topic? I can point to a Japanese language document on this but that won't be very useful I fear...