KSR19 5-in-1 robot

I build the KSR19. Had a lot of fun building it. I tried the pen-module first. Thats when I encountered some problems…
Some of the coding buttons (E7) do not work, they are not touching the knob (B5) enough. The robot does not go backwards, it stops. The knob is not pushed down far enough.
Left and right turns are not working properly. Forward left does not work. Coding button E8 does not touch the “brake” enough to turn.

Maybe if the coding buttons were somewhat longer.
The coding wheel does go round fine, so that’s not the culprit…

I am a bit disappointed by this, I bought 3 of them for my school and a not properly working robot is very frustrating for students.
What to do?