Ubuntu 17.04 XFCE4
When I log in to the computer, Control+R works in all programs. However, after some time (usually after some inactivity, even though the computer never sleeps, the monitors just power off) it stops working in all programs (ex. neither Chrome nor PHPStorm will respond to it but the respective actions it would normally trigger in those programs works when activated froma menu). All other shortcuts work fine, it seems to be only Control+R that's affected.
In the system "Keyboard" settings there are no application shortcuts bound to this combination.
I have run xev and verified that the output is the same when the combo is working and when it isn't.
All I have to do to correct the problem is log out and back in - a system restart is not necessary.
Since the system is recognizing the keystroke but no apps are responding to it, I'm assuming some running process is hijacking this combination, but I don't know how to find out which application that is.