I just had this happen, it also happened twice yesterday.
Right now I'm going to say it has something to do with creation of a new window (maybe tab as well). Whether its mouse or key combination both seem to be affected. Issue doesn't happen every time I create a new terminal window / tab.
First solution was to logout and back in but I've since found that finding and terminating the xfce4-terminal process (there are 2 on my machine, this time I killed the one with an icon in system monitor and it also shows memory usage the second process shows the memory usage as N/A). This obviously killed my terminals but when I opened it back up the terminals work fine.
I just had this happen, it also happened twice yesterday.
Right now I'm going to say it has something to do with creation of a new window (maybe tab as well). Whether its mouse or key combination both seem to be affected. Issue doesn't happen every time I create a new terminal window / tab.
First solution was to logout and back in but I've since found that finding and terminating the xfce4-terminal process (there are 2 on my machine, this time I killed the one with an icon in system monitor and it also shows memory usage the second process shows the memory usage as N/A). This obviously killed my terminals but when I opened it back up the terminals work fine.