I suspect based on anon958860’s wording that they attempted to change the 3 letter code either in PT or in the Registry. If you try to change it in PT you will see a message telling you that it can only be changed in the Registry–but you’ll also see that the short name is grayed out, indicating that it can’t be changed. If you go to the Registry, you’ll find that you can change the full name, but not the short name.
As points to in his , the only (?) way to change the short name is basically convert the project into a new project. This is not particularly difficult, but it does take a bit of coordination because it requires everyone to do a S/R, delete their project, one person to convert it and re-register it with the Registry, and then to share the “new” version back to the team.