When any underlying data changes, even if the document itself remains the same, the system will mark the document as needing re-generation. This happens because Ketryx ensures that all release documents are up-to-date with the most current data by taking a more conservative approach. Although it seems like no changes have been made based on the content of the document, underlying changes have been made in the project. 

If a configuration item is updated, and it includes a field that isn't displayed on the document, the document will still require regeneration. This leads to the behavior you're observing where two documents may not show a meaningful difference, but Ketryx still requires them to be re-generated. The underlying data changes can include referenced project data.