[openbox] Cannot use keyboard sometimes after changing desktops

[Dani]

I usually change between desktops quite rapidly and often it happens
that after changing I cannot use the keyboard to interact with windows.
Nothing happens to the windows when pressing keys. The problem goes away
after changing to some specific desktop. Usually I simply cycle through
all four and then I can write again. Why does this happen? How can this
be prevented from happening?

details:
computer: HP Pavilion dv7-6025
operating system: Parabola GNU+Linux-libre
video driver: radeon
X.Org X Server 1.18.2
OpenBox 3.6.1