Aux bus affected by changes to output bus

Question

UE4 4.20; Wwise 2018.1.4.6807; Windows 10

I have a 2D sound object playing out of its own output bus that is also being sent to a separate aux bus with 3D positioning on it. In engine, everything seems to work properly except for the fact that any changes made to the output bus also seem to affect the aux bus. For example, when an RTPC raises the value of the LPF on the output bus, the sound from the aux bus is also low passed. Is this some undocumented behavior of aux busses or is there something I might have accidentally set to have caused this?