I have been told that shade on part of a panel affects all the panels connected with it. Is this true?
Back in the early days of Solar Energy Systems shading on any part of a solar panel would render the panel inoperative. Shading did not only affect the panel in question but the whole string of panels it was connected to.
Todays solar energy panels have bypass diodes integrated into the panels. The bypass diode (as the name suggests) bypasses any shaded inoperative part of the panel allowing the rest of the string, and in many cases the rest of the panel where it is only partly shaded, to continue to generate electricity. Bypass diodes can fail. In some panels the diodes can be replaced in cheaper brands they can't. As they say "you get what you pay for"