AltGr key released when rapidly pressing other keys

I have a Norwegian Lenovo USB keyboard. When I hold AltGr and press v and b rapidly, it produces “bvbv instead of “”“”“”. I get the latter expected result when pressing v and b slowly. Never letting go of AltGr. xev shows that the AltGr key is released when pressing b for the first time when doing this rapidly. (Output .) Any idea what could be causing this? Updated Debian Jessie with GNOME desktop.