Hi Bart,
thanks for your answers. As for your old problems with Ubuntu, as far as we know all problems related to the synchronization of toggle keys should be fixed in the last version (BTW, I see you are using a quite old version on client side, various bugs have been fixed since then).
Regarding the issue with NumLock, here are a couple more links that confirm this has to be considered a bug in Mate:
https://bugs.launchpad.net/ubuntu-mate/+bug/1364111
https://github.com/mate-desktop/mate-settings-daemon/issues/57