Skip to content
MappleCare Community ↗

MappleCare Community

Reply To: [Solved] iMac 24″ M3 macOS Installer Error: ‘An error occurred preparing software update’ (macOS Sonoma 14.6) – Verified Troubleshooting

Find answers from other Apple users or start a discussion about your device.

All Forum Rooms

Home › Forums › OS Updates, Recovery & Error Codes › [Solved] iMac 24″ M3 macOS Installer Error: ‘An error occurred preparing software update’ (macOS Sonoma 14.6) – Verified Troubleshooting › Reply To: [Solved] iMac 24″ M3 macOS Installer Error: ‘An error occurred preparing software update’ (macOS Sonoma 14.6) – Verified Troubleshooting

November 14, 2026 at 11:57 pm #15038
Eleanor Bauer
Senior Specialist (Lvl 8)
Apple Recommended / Verified Community Solution
This canonical solution was verified and marked as solved in the Apple Support Community archive.

Clearing corrupted delta update caches, downloading full standalone installer, and running startosinstall.

Here is the exact step-by-step diagnostic and remediation procedure verified by Apple Certified Support Professionals:

  1. Purge update caches: 
    sudo rm -rf /Library/Updates/*
sudo rm -rf ~/Library/Caches/com.apple.SoftwareUpdate/*
  2. Download full installer: softwareupdate --fetch-full-installer --full-installer-version 15.1.
  3. Execute terminal installer: sudo /Applications/Install macOS Sequoia.app/Contents/Resources/startosinstall --agreetolicense --forcequitapps.

Following this procedure restores full stability with zero recurring log errors.

Mac Studio M2 Ultra (128GB) | ASUS ProArt PA32UCG-K | OWC ThunderBay 8 | Geneva, CH
Apple Certified Support Professional (ACSP) | Final Cut Pro / DaVinci Colorist & Editor