There is a bug within the backup and restore of user field conditions for modules and sections.
Presently when backing up a user field condition if its a custom field the id of the field is recorded and then upon restore we check that a custom field with the same id is checked for existence.
The problem is that id doesn't identify the custom field, theres nothing to say that custom field 5 is the same on sites a and b.
Really we should be recording something more meaningfull, like name, and then searching for and mapping that upon restore.