PHP 8.2.10, Phorge at `7868ab3754fad13714640451d664d5bc71b7a02f`.
**Steps to reproduce:**
1. Go to http://phorge.localhost/project/edit/form/default/
2. Create project with name `Slug404Name`
3. Successfully go to http://phorge.localhost/tag/slug404name/
4. Select `Edit Details` to go to http://phorge.localhost/project/edit/23/
5. Rename project to `Slug404NameAlt`
6. Successfully go to http://phorge.localhost/tag/slug404name/ which redirects to new primary slug
7. Select `Edit Details` to go to http://phorge.localhost/project/edit/23/
8. Remove `slug404name` from `Additional Hashtags` && in the `Name` field replace `Slug404NameAlt` with `Slug404Name`
9. Go to http://phorge.localhost/tag/slug404name/
**Expected outcome:**
Project page is rendered
**Actual outcome:**
404 error
**Other comments:**
* Explicitly adding the already-primary slug `Slug404Name` to `Additional Hashtags` on http://phorge.localhost/project/edit/23/ makes http://phorge.localhost/tag/slug404name/ work again, as assumed in https://phabricator.wikimedia.org/T224662#5223847
* Might not be the only one to reproduce but finally a way to reproduce. Upstreaming from https://phabricator.wikimedia.org/T224662 as we've ran into this several times.