When you have two apps with the same content-type and wish to sync the fields from a Source to a Target, do this:

Before you Start

Ensure that they have the same Static Name. If they don't you must:

1. either update one of the Static Names
2. ...or skip this and Update/Synchronize manually

Do the Update

1. Export the schema from the Source
2. Import it in the Target
3. Review the fields in the Target content-type, ensure it matches your expectations
4. Test the result