Shade effect on series panels.

Mismatched panel Vmp: Unlike batteries in series panels have non linear voltage which is shown on the IR curves for the panels. Since a MPPT controller maximizes the total power by adjusting the (panel) load some serial panels produce less amps then their irradiance would indicate. And they may not be at their Vmp since the total series string is not optimized and can’t be optimized for every individual mismatched panel.

There seems to be little information on this subject. Possibly because solar arrays tend to use matched panels vs DIY projects which often evolve over time.