Shift-clicking it in causes it to go back to storage, and I can't put it in manually. Help on this would be appreciated.

this is something you will have to ask neeve to support in nae2, not here. it doesnt go in the dual interface becaues the dual interface doesnt support it. Also I hope your aware that a regular interface can output fluids so you dont actually have to use a dual interface.

oh, alright, my fault