As I am not sure of the real issue here, please bear with me.
Yes, I do understand that there is an issue, however, I do not claim to know how to fix that particular one.
That being said, I suggest trying the following-- if for no other reason but to give me feedback.
First, let me know if you are targeting a single potion and this issue is occurring.
Note: if that is the case disregard the following and have a swell day, cause I haven't a clue.
Second, if you are targeting a stack of potions, try taking one out of the stack, and then use the gump to target the single potion VS. the stack. Also, be sure to keep the single potion and the stack of potions, of the same kind, in your main backpack when trying this test.
Third, feedback would be great.
My thought is that the code is written in such a way that the gump is looking for a particular value, versus looking for a value and the values sum.
So, for example, if you have two 2010 Mustangs (potions), one being metallic dark green, and the other is metallic blue, ready for pick up at a dealership (potion storage location). Consider the "gump" the pick up driver who has orders to pickup (use) a 2010 Mustang from the dealer ship. When the driver (gump) gets there he doesn't know which one is the one he is supposed to pickup (use) because there are more then one 2010 Mustangs to choose from. Now realize that the driver (gump) is programed in such a way that no matter (by default) what the situation is he can not make a mistake (software error). He has no choice but to take all (by default value) the choices possible, and deliver them to their new destination (plant).
This same problem occurs with storage keys, or once did. The green token gems collected form killing certain mobs in the newbie dungeon have the same value as an arcane gem, but their sum-- in this case their color and name-- is different. So, when you use the adventuring boots storage keys and have both kinds of gems in your bag, both are collected, and considered arcane gems.
I could be totally wrong, it is 1am and I kind of wrote a book, but it looks good an I'm going with it.
--Sturger--