All applications got paused after disk space usage got near 99% and back to normal. What's next?
To un-pause those paused/not responding applications after you free up some space, try to run this command:

pkill -CONT -u $UID


or (as suggested here):

kill -CONT -1


If this happens very often, consider adding the following alias into your shell rc file, e.g.:

alias unpause="pkill -CONT -u $UID"