Recently on a server I noticed that Personal Safe shift-clicking could probably use an improvement, specifically in the way that it does not work quite like how a chest works.
Example: I am trying to shift-click item E into the safe so that it stacks with my Item E that is already in there
>>> = addition of Item E
Chest:
Scenario 1. [A6] [B45] [C60] [D12] [E] >>> [A6] [B45] [C60] [D12] [E2]
Scenario 2. [ ] [ ] [ ] [ ] [E] >>> [ ] [ ] [ ] [ ] [E2]
Personal Safe:
Scenario 1. [A6] [B45] [C60] [D12] [E] >>> [A6] [B45] [C60] [D12] [E2]
Scenario 2. [ ] [ ] [ ] [ ] [E] >>> [E] [ ] [ ] [ ] [E]
As you can see, everything goes in properly when Item E has no empty cells before it in the safe, but when there is an empty cell, unlike a chest, Item E will fill that empty cell instead.