Ctrl&Shift&Alt randomly get "released"

[Oscar Jonsson]

I'm using Linux Mint 18 'Sarah' "Cinnamon 64 bit"
The problem I'm having is very frequent and seems to have been since installation of linux mint, often occurring with only 1-3 seconds between. Other times it seems to take a break for minutes and then everything works as expected.

It is the same with alt, left shift, right shift, left ctrl, right ctrl.
I *don't* think it does this with alt gr, but I'm not 100% sure.
What happens is that I hold one of these keys down and the computer randomly acts as if the key has been released even though it hasn't.

Some examples:
I highlight a bit of text, then press ctrl+C to copy but before I've gotten to the C the ctrl has been released and the highlighted text is instead replaced by a c.

I hold shift and use the arrow-keys to select text, it then acts as if shift is released which makes the text getting de-selected on the next stroke of arrow-key.

I do alt+tab to change window and alt gets released and the window-change is interrupted.

Really quite annoying =)

This is the first time I've installed Linux on this computer so I don't know if other versions/distros are affected.