Keyboard problem (key "4")

I have a very strange problem with Guake. I'm under fedora 27 (wayland/gnome 3.26) with a bepo keyboard layout (but it doesn't change if I change the layout).

When I start Guake, about half the time, the number "4" is not recognized. I can't even type it. The cursor blinks but does not display any characters. If I leave Guake and start over, it works normally.

It's very painful because it's random.
Do you have any idea where the problem came from?
Thank you in advance.