With the meter across the leads, I get 255mA and 6.5v
I guess it is me that is not being clear.
That is a valid way to measure voltage, but not a valid way to measure current.
The load presented by the meter is different in current measuring mode than in voltage measuring mode. If you had two meters connected at the same time, you would see that the voltage is not 6v when you measure current that way. If you really had a 6v voltage drop across your meter when set for current measurement, you would probably see smoke coming out of it (!)
Once again. To measure the current under load.
1) connect everything as for normal operation. (panel, battery, Minty & phone)
2) disconnect one of the wires from the panel.
3) set your meter for current measurement and touch the probes to the disconnected ends of the wire to complete the circuit.