Using Manual Mill only generates 15.04 GP. Resonator needs 16 GP

You can just use two manual mills (switch quickly from one to another), although I'm not sure what the intended solution is. Either way, I think that's an XU2 problem.

The resonator only needs 8 GP for some items, including ones that you can use for automatic GP generators. I guess making them is the intended path.

Tested; the components for several mills can be crafted using the power from a single Manual. No bugs here.