Maintenance for the week of July 13:
• PC/Mac: No maintenance – July 13
The issues on the North American and European PlayStation® megaservers have been resolved at this time. If you continue to experience difficulties at login, please restart your client. Thank you for your patience!
For Steam at least, Steam installs a very old client/installer and downloads the full game to one location and then the installer wants to copy (not move) these files to another location, making you have two copies of the game. I don't recall if the installer files get cleaned up. Do not use Steam to verify your install as it will revert to the very old files, requiring the ESO Launcher to redownload the files.