In September 2018, I bought a new “display-o-tron HAT”, but not at pimoroni shop. In February 2019, I tried it out the first time, and noticed that LED 0, 3 and 4 of the backlight (all three channels R, G and B resp.) are dark. Even the R channel of LED 5 seems to have a slack joint, sometimes it’s even dark too. Despite this, the display works as expected. All pins on the back look soldered well. What can be the reason of that? Does the backlight consists of a typical shift register RGB like WS2812? I have good soldering equipment and a lot of experience, should I desolder the display in order to have a look at the SMD-LEDs behind it? Is there any schematic available?