Current shunt reading weird?

I have a little kit I bought online with a current shunt and an LCD display. For some reason, the way I have it wired, it reads over an amp of current when I know it's way, way less, and when I add another load that should draw over an amp, it decreases the readout, saying more like 600mA. What would cause this? Is it just liable to be inaccurate at extremely low currents, or do I have the readouts backwards, or is there additional resistance where there shouldn't be that's causing a voltage drop?

A few details could help. Name of kit/model no?

Here's the kit:

Sidenote, I had it working not long ago, but I had to transfer all the electronics to another container. I'm also having some of the wires shared, but it's occurring to me now that I probably shouldn't. I just realized I had a load on the wrong side of the current shunt. I fixed that, but no change. I put my DMM in series with it the circuit. DMM says 1A, shunt kit says 0A. DMM says 3A, shunt kit says 2A, and DMM says 4A, shunt kit says 2.65A.
I'm gonna redo it so every wire is dedicated for the shunt kit and see if that fixes it (I bet it will).

Yeah, sharing two of the conductors was messing up its read. It's fixed now.