Manually placed DataGroup Annotation Cells disappear on reopening of the DGN file if "Enable Auto Annotation" is turned on..
User needs to use a combination of auto and manually placed DataGroup Annotation Cells.
Check the configuration variable, BB_AUTOANNOTATION = manual. Also, be sure that the variable is spelled correctly if it is defined in the project.pcf file. If the variable name is not correct, the "Enable Auto Annotation" option will not be removed from the Building Designer pulldown menu and can still be accidentally turned on. If this occurs, it will remove any annotations from elements in the file since there is no rule applied for them.