After assembling the kit successfully, the screen and sound worked fine and the kids enjoyed playing with it for a few hours. However, from a certain point, the kit refused to work: the screen backlight worked, but there was no picture, neither sounds. Reading solutions to similar problems reported on the forum, I tried the “C button trick” – and it actually worked: the screen and sounds came back to life.
Unfortunately, the screen started to show a few blank horizontal lines on the bottom. I tried to re-attach the screen, refine the solderings [double-checked with multimeter], but the screen keeps showing a few blank [dead?] lines on its bottom - as seen on the attached photo.
[you could notice that the serial programmer header is not soldered, because it was not included in the kit - but that’s another issue]