On Saturday 16 January 2016, Thierry de Coulon wrote:
> There is on thing however: there is a USB switch between the keyboard and
> the computer. I'd have to test if this happens on the other computers
> connected, but I seldom have to use these keys on them because they have
> special uses (video, backup).
>
A few days ago I noted, that I have the same problem and I was - at least - able to get AltGr 
behavior back (without logging out and in) by un-checking the "Enabled Keyboard Layouts" check 
button.

Now I see that there is something in comon between us both. I also use an external USB switch, to 
switch keyboard and mouse between a Windows and a Linux system. I use it very seldom, for sure not 
before the problem happened. But who knows ...

I furthermore mostly don't shut-down my system but put it into the Suspend state. My assumption is 
that sometimes it does not correctly re-initiate all parts of the system when coming out of 
Suspend.

Gerhard