Before comparing replica schemas, ensure that you can preview the data in both the parent and child as the replica ownerIf the data source is broken in the parent and an attempt to repair the data source produces a 'schema out of date' error, - preview the data in ArcCatalog as the data owner to update the schema, then verify that data source is repaired in ArcMap. Alternatively, the data owner can change the data source to user data owner's connection; then change data source back to replica owner's connectionOnce the data source is repaired, proceed with compare replica schema step.