Are there any button settings on the converted file's container field?
Did that same file work as expected in earlier GO before conversion?
Compare how the file's container storage options are set in the converted file and the FM 12 new file. See
- File > Manage > Containers...
to compate the settings on the two files.
If you are using custom menus, you'll need to redo the Insert menu because new items where added in FM 12. The contain fields will not work properly until you fix the custom menus.