unknown update error

@fallenimaginary  Do you use a third-party antivirus?  If so, please disable it, then clear the EA App's cache and try to repair Sims 4.  Then try to run the update again.

If this doesn't help you might need to do a clean uninstall and reinstall of Sims 4 and the EA App, or at least it might be quicker to do that than to keep trying other less reliable interventions.  Start with Sims 4:

• Put aside your Sims 4 folder in Documents\Electronic Arts and rename it to something that doesn't include the words "Sims 4."
• Download Revo Uninstaller (the free version is fine) from here.
• Launch Revo, select Sims 4 from the list, and click Uninstall.
• Once the game is uninstalled, select "Moderate" under "scanning modes," and click Scan.
• Review the list, in case there's something you want to save; otherwise, click Select All, and then Delete.
• Close Revo, and restart your computer.

Uninstall the EA App with Revo as well.  I don't have instructions for that at the moment, but the process should be straightforward.  Restart again when you're done.

Install the EA App, then create a new folder into which you'll install Sims 4.  The folder should be on the root level of the drive of your choice, for example C:\Games is fine, but not C:\Program Files\Games.  You can install only the base game, to save time, if you want.