Here are my usual control bindings:
![Image](https://forums.factorio.com/images/ext/30c2de5e237ba86f07e225aed6340ae0.png)
When attempting an Inventory Transfer, items instead move as if I were doing a Stack Transfer. I expect all my inventory of the same type to move when I shift+Mouse5, but instead all my current stack moves.
The Inventory Transfer works as expected if I delete (or set to anything besides the mouse button used for Inventory Transfer) the Stack Transfer binding like so:
![Image](https://forums.factorio.com/images/ext/02c8ceff5dfff5f0d008d870c90fa020.png)
I've repeated this with a character inventory to a car inventory, train inventory, and chests. Note that I use a similar control scheme for the Inventory Split and Stack Split bindings, but they behave as expected.