OK, solved that one panel. Now I may debug the others a little.
Funny story: I wanted to check the LED collars as you suggested, but didn’t know what these are. So I googled “LED collars.” I don’t have a dog, but if I ever want to know what I need to walk one at night, I now have the answer. It brought me no closer to the solution though (but I figured it out).
The issue was some of the points where I soldered the leads – some were barely soldered in and one or two were black.
Thanks, by the way, for the help.