After receiving this message I binned the installer and attempted to download it in safe mode as suggested in a previous discussion but the same problem occurred. Any ideas?
That error message typically indicates that the Apple App Store is detecting another copy of the macOS Installer is still on your Mac's drive (by default, it is placed into the /Applications folder.) You said that you deleted it, but did you also empty the Trash afterwards? Just wanted to make sure you didn't miss a step.
I'm not entirely sure what exactly to do but you can try these steps :
*** Only do this if you want your data gone. ***
1 - Press cmd-r when the iMac starts to boot up
2 - Open MacOS Utilities and re-install the MacOS that was there by pressing Reinstall MacOS
I am going to offer the following to consider. It may be that subsequent downloads also got corrupted in the download process, especially if you are using Wi-Fi. It is simply often too slow for these very large files and corruption occurs. You can keep downloading until you get a clean download file or try using a wired Ethernet connection for the download. Then all should go well. I hope that helps.
Reinstalling the system from the Recovery volume does not affect the user data:
If you first erase the drive with Disk Utility then the user data is lost.
This copy of the Install macOS Ventura application is damaged and can't be used to install macOS
