Look through all the translation pages, and try to find those that say that the translation is incomplete, while actually it's all done. After you find such a page, do an edit (a real edit, earlier it was enough to do a null one to purge the page) and save the page - you will notice that the translation is 100% complete. The stats are not updated as expected due to some bugs. As for this one, I've already filed a task on phab:T106262
This one shows 98% complete. Do another small edit to make it 100% complete.
Excellent - thank you all. Turns out each subgroup is now at 100%, at the main index at 99% - assuming it's just a matter of waiting for the stats to update. I'm excited to be part of this project!
Thanks everyone for participating! I'm already planning the next one ;) Stay tuned for updates,