It seems like dosbox is only emulating 2 controller buttons.
Input: force 2-axis/2-input doesn’t appear to be working properly. Even disabled, dosbox acts as if there are only 2 gamepad buttons. enabling/disabling this doesn’t have an effect either way.
@Jamirus
you use dosbox, right? Need someone else to confirm this before posting an issue on Github. 
Due to the joystick hardware limitation of only 2 buttons, you need to disconnect all other joysticks in order to get the 4 buttons on the first and only gamepad.
there’s only one joystick connected, though.
edit: okay, got it working. It’s not enough to physically unplug them, you have to set the device type to “disconnected” for the other ports (settings -> input).
Aye, I could have been clearer, and indeed it has nothing to do with host-side physical controllers.