This curve was taken around noon with the panel laying flat. The maximum power point corresponds to a load of about 100 Ohms. Note the maximum power of 1.4 Watts, and even when the panel was oriented perpendicular to the sun, only 1.6 Watts were reached. The panel is advertised at 4.2 Watts - What? Could it be that the traces on the PCB are too thin? The Molex connectors too high resistance? Time to redesign the PCB, and to try XT-60 connectors or screw terminals?