Project apparently disappeared after upgrading to 8.15.4

I'm using gitlab ce in my office and never got an issue like this while upgrading.

I've a namespace named "CMS" where I've a project named "files". After upgrading from 8.14 to 8.15 the project apparently were moved to files0, but it shows a "no repository" page:

Started GET "/cms/files0" for 172.17.0.7 at 2017-01-16 14:00:46 +0100
Processing by ProjectsController#show as HTML
Parameters: {"namespace_id"=>"cms", "id"=>"files0"}
Completed 200 OK in 143ms (Views: 80.2ms | ActiveRecord: 15.9ms)

If I try to access its previous location, it shows me a 404 page.

Started GET "/cms/files" for 172.17.0.7 at 2017-01-16 13:54:33 +0100
Processing by ApplicationController#route_not_found as HTML
Parameters: {"unmatched_route"=>"cms/files"}
Completed 404 Not Found in 15ms (Views: 0.4ms | ActiveRecord: 1.3ms)

I've run both gitlab:check and gitlab:repos:check, both run successfully plus I can see in the logs that the project is always named cms/files, never cms/files0.

I've tried upgrading the path field for the project's database entry related to this project, but then I get 404 on both files and files0.

I'm not sure what happened because I can't see in your changelog any entry related to setting files as a reserved project name, so I've no idea what's going on.

Any help on how to fix this would be much appreciated.

If I need to extend my information with some kind of log, please, tell me and I'll add it.