After building and running engine-q, I cannot type { or }.
I use an italian keyboard, where opening and closing curly brackets implies pressing: Shift + Alt Gr + Key.

Note that even just typing [ or ] seems to present a problem, and it implies pressing: Alt Gr + Key.
In this case, the square brackets are printed, but they can only be cancelled by pressing Backspace twice; it looks like "two characters were pushed" instead of one.