MK124 - top line of LEDs not working

The rolling message is all working fine - except that the tops of the letters are missing!

Since the whole row does not light, I assume the problem is something other than the LEDs.

I cannot see any shorts with my old eyes. My soldering is not great, but seems to work, except this.

Can you tell me which component would cause this failure?

Many thanks.

Sorry to say, but most likely an assembly problem is at the cause of troubles.
Hereby the diagram and PCB layout, to allow troubleshooting.
Sorry, this forum does not allow picture uploads
If you can provide LINKS (e.g. by using a free online picture base) to HI-RES and SHARP pics of your assembly (both solder- and component side)
then we can take a look and provide some feedback.
Should you be unable to solve the problem, then you can return the kit for inspection/repair.