This happens to me quite often, but not on a regular/daily basis. Out of a week, it may happen on two or three days, and sometimes a few occurrences on that day. Sometimes just reconnecting works, and other times, I have to actually exit out of the Operator Client and restart the Operator Client. Also, I find that if I leave my Operator Client connected for a long period of time, I get this issue too. By "long period of time", I am suggesting in excess of 8 hours.