When I restore a full backup or migrate a domain root to root, when it arrives at the restoration of databases, it starts to restore but never ends, is running the points on the screen, and the only way to end it I saw ssh console and kill the process that makes the restoration of databases, complete and then he goes to the next steps. In the process I noticed that one is named "defunct" with the same start time of the process that restores the database. This problem occurs on all my servers (10) but in new servers does not occur only after restoring a 500 area then begins to happen on the new server too. What can this be?