Someone left the organisation but before leaving, he locked all the files for an unknown reason.
How do you unlock them all so that the other developers can work?>
Sometimes this is masking an different problem with a completely different application is locked by another user, but you cannot even create a New Folder for the new project you wish to merge into ( target won't allow the creation and incorrectly stating that someone has a file locked in their name) but then you dig deeper and another project is the culprit.
So a completely different project can be the problem with it having files locked by someone else.