No keysyms send on level 7+

[Adam Nielsen]

> This last point make me think it is maybe related to my hardware ?
> It is something knowed that we can't abuse at will of the last layers?

Have you tried plugging in a second keyboard, and pressing half the
key combination on one keyboard, and finishing it off on the other?

That should tell you whether it's down to a hardware limitation on the
keyboard itself.

If so, you can look for one of those special n-key rollover keyboards
that have no limits on the number of keys pressed simultaneously.

Cheers,
Adam.