In the backport of http://gerrit.ovirt.org/#/c/25022/ there was a bug introduced by using the variable name 'migration_progress_timeout' which was not part of the backport in config.py. This causes the Migration monitor thread to prematurely exit.
This is an automated message oVirt 3.3.5 has been released: * should fix your issue * should be already available at your local mirror If problems still persist, please make note of it in this bug report.