Gnoll scroll drop percentages

[Ooloo]

So I've been farming gnoll scrolls as kind of an experiment to confirm or deny that one particular scroll is more or less common than another, which has always been a rumor. I'll often see people insist that #1 is more rare.

After farming them extensively for a few days it seems like they all have roughly an equal 25% chance to drop provided you don't already have a scroll. However, about 80% of the time once I loot a scroll, regardless of which one it is, the next scroll I attempt to loot will be a duplicate of the first one and thus I can't loot it cause they're lore. Often, even the 2nd or 3rd one I try to loot will still be a duplicate, which seems incredibly unlikely. If they all have an equal 25% chance to drop, it should be a fairly rare occurrence that the 2nd scroll you loot is the same as the one you already have, but instead that seems to happen much more often than it doesn't.

Is it possible there's some piece of code that scans your inventory, and if you already have a scroll or scrolls, the next gnoll you kill will be more likely to drop the one(s) you already have, maybe to discourage people from mass farming them for the xp? Cause just statistically it seems really strange how they drop. Granted it could just be really bad luck on my part, but having farmed them for multiple days now I think I have a decent sample size.