It's a sign that someone in the congregation is practicing secret sins. They should keep giving service talks about not concealing sins, and the need to confess to the elders so that the evil person that is causing these problems can be removed and no more natural disasters befall the Kingdumb hall. If they don't take care of it the next thing Jehovah might do is to cause many brother to start losing thier jobs, if that don't smoke out the the evil doer then he might cause a bad case of hemroids to devastate the congregation, next leperousy, and plague of locust.
.