When a source page, that already has existing translations, gets modified and then marked by a Translation administrator to incorporate changes, the individual resources are processed to find those that may become fuzzy and would be needing changes.
However the translation status and statistics (number of translatle items completed in that page) if not updated at all, and none of the translated pages are refreshed.
There should exist a programmed task to regenerate these pages, or if this is not done (because the result could be a strange mix), at least the status and completion statistics should be updated.
An example is the translation of Tech news on Meta, which is created in a fast process which frequently requires several updates while translations have already started to be created. We find then som intermediate versions that were completed 100% in a prior version, but left at 100% (also with their "Ready" or "Published" status) when they should go to a lower completion score (also with a status changed back to "needing update" if there's some fuzzy item, or missing item).
Current work around:
After a translation admin marks a new version to translate, it should review the existing list of languages, one by one, to perform at least one null-edit in one existing item; or by looking for an item which can be relaiably translated from the translation memory with 100% match (e.g. frequently reused items like headings, such as "See also" or common Wikimedia project names used in lots of translated resources, or common UI elements like "Save" buttons).
To perform a null edit: select the item to edit it, press the END key or click at end of string, press SPACE, press BACKSPACE to remove that SPACE. Then save the item unchanged. This is enough for the Translate extension to refresh the translated page and its status, without even making any change.