We observed, by complete accident, that when a stack of Acid Bottles is collected, from an Acid Puddle, and then the stack is split, no matter whether it is a single bottle out of the stack, or half of them, all of the bottles from that stack after that will stop counting as "Lair Resources" and will no longer grant points, or be recognized as such.
This might also be the case with similar resources, such as Tar Bottles, that act in a similar fashion.
Of course, the easiest work-around is not to split the acid bottles, but sometimes when you want for multiple people to get a bit of "Resource" XP (especially when they helped gather the acid or tar) a bug like this makes it impossible.
When you split a stack you strip the items of it's variables. Nothing much to be done save making the items not stackable (but why not...)
Just have different people pick up the ressources.