When adding more fluid_boxes to an entity of type assembling machine, setting the `production_type` on the fluid_box is limited to be input or output, it cannot be input-output (I assume this is the part that changes the symbol indicators).
However, setting `type = 'output'` or `type='input-output'`on specific pipe_connections makes the fluid_box act as it normally would, with the incorrect indicator.

In the above image, fluid is allowed to flow from north to south, while showing the indicators that the assembling machine can only receive fluid.