If there are too many class AddonsMetaData entries in a NON binarized mission.sqm file briefingname is not being read but instead the mission filename is shown in the mission overview in the server lobby.
A mission with just one entry in class AddonsMetaData is fine, briefingname gets correctly displayed.
I guess the routine which reads in briefingname stops if it doesn't find a briefingname entry after a specific number of lines in non binarized mission files