Partial panel background

I have chained three 16x32 panels (Adafruit) to a RPi 2 B which has been behaving fine for several months. I occasionally move the panel a bit, and now when executing a program it is showing a persistent partial panel background color across two panels different than the code. All wiring looks good, so what could be the cause? It started with one panel, now it is two.

panel

if you put the last panel first and the problem remains, you may have a short in the back of the panels