Big Sur 11.5.2 Update fails to install

Check in Applications folder for an existing Install Big Sur. If, Yes, Drag and Drop to Trash and Empty Trash.

If this update is for Big Sur 11.5.2 the error message can be misleading. There are factors like poor Wifi connection, slow wifi connection, too many other people downloading at the same time and Apple Severs are overloaded, Software on the computer interfering with the download process, running behind a VPN and or / if via wifi too many Other devices using the wifi at the same time reducing the Bandwidth to you computer.

Best Results are via Ethernet Cable to Router

There are several ways to download the Big Sur 11.5.2 update. 

1 - Connect to Router via Ethernet connection and restart the computer in Safe Mode and then open the Apple Apps Store and get the Full Installer of Big Sur. It will be the 11.5.2 version and once downloaded run the installer from the Applications folder.

2 - Resart the computer in Recovery Mode ( INTEL Command + r ) and choose Reinstall macOS. It too will download the full Installer and commence the installation. For M1 CPU the Recovery Mode is Here

3 - This method may seem unnecessary but sometimes the Router Restart clears Network issues from ISP to Apple Servers

Shutdown Router. Shutdown computer and disconnect all External Drives. Restart Router. Connect to Router via Ethernet Cable. If via Wifi - Disconnect all other Devices using the Wifi - want the Maximum Bandwidth only for this computer. Restart computer in  Safe Mode. It does a Repair Disk, Clear System Cache files and only load Apple Software, extensions and Fonts. Will load slowly - Normal. Once Logged in - open Apple Apps Store and  Get the Full Version of Big Sur. It will take some time and several pauses will occur - normal. Countdown clock may say 15 minutes but in Real time may be 30 minutes. Same goes for clock at 10 minutes could be 20 minutes in Real time. Eventually , Full Installer will download and a New Application in Applications Folder will present called Install Big Sur. Stop there and perform a Time Machine Backup. If desired - have an External Drive - Copy & Paste the Install Big Sur Application to external drive for future usage - making a Bootable Installer. Now run the Installer.

Have found this method more reliable than the Software Update which is very iffy at best

Are there any AntiVirus, Disk Cleaner, Optimizers, Defrag, VPNs etc installed which should be removed as per Developers Instructions. They are useless, unneeded, cause havoc and interfere with the normal operation of the OS and may even Corrupt the OS requiring a Reinstallation.

To perform this action will require booting from a Bootable Installer. This will have to be performed from a Qualifying Computer to run the version of macOS to be made on the Bootable Installer. Example : Bootable Installer of Big Sur would have to be done on a computer that Qualifies to run Big Sur.

How to fix a split Fusion Drive

Once that is done read on for preparing the Destination computer  >> Special Notation - works on Intel Based Apple Computers & May on Apple Silicon M1 CPU

Extra Special Notation regarding the Touch ID equipped Apple Computer. About Startup Security Utility and Must Enable from Recovery Mode the ability to boot from External Drive Before Attempting 

1 - Shutdown computer and disconnect all external drive Except the newly created Bootable Installer.

2- Restart and immediately hold the OPTION key until the Startup Manager appears and choose the USB Drive. 

3 - It will present options >> Disk Utilities >> View >> View ALL attached Drives. 4 - Choose the Upper Most Drive ( not the volumes indented and list below ).

5 - The drive normally is called Apple Media or Apple SSD - that is the drive to Erase and format as APFS with the GUID Partition Map. 

6 - Once that is done >> backup out of Disk Utilities and choose install macOS. 

7 - Follow the prompts and it may automatically reboot several time. 

8 - Upon a final reboot - Setup Assist will present with the newer version of macOS.

I didn't update to Big Sur 11.5.2 after hearing from a friend who said it was the worst, saying "It has slowed my Mac down so significantly, especially when I'm trying to watch/stream any kinds of shows or movies. So I am backing everything up, I'm going to wipe my Mac and reinstall Catalina. I've never had to do this ever with any Mac OS until now. Nightmare!"

Sorry, Big Sur 11.5.2 is terrible. I have been trying to get my iMac back to shape for over a week now. That update almost froze my computer, launching Final Cut Pro took 43 minutes, created a new account, it took 1h 20min to log in and the list goes on and on. Reinstalling .2 made things even worse, crashes without a clear cause, nothing written to the log files. So, I wouldn't recommend this update.

Now I'm trying to get 11.5.1 installation files to go back a step. There is a backup in time machine, but it is unusable for downgrading. So, it's time for a build a boot USB session.

Hello P. Phillips,

I will try to follow some of your advise.

My problem was after updating to Big Sure 11.5.2, I couldn't start Norton antivirus or VNP. So I called Norton support who removed Norton from my iMac via Terminal and wanted to reinstall it. They failed to reinstall it, but while keeping trying, after 2nd restart, I lost internet connexion. Now what I have is no internet access althouth the network screen shows ethernet connected, wifi connected, and Norton 360 starting. So the worse part is loosing the access to internet.

I will try you point 3, not not sure it works.

Hi P.Phillips,

thanks for the guide, I made the installer yesterday and I'll do the install this evening (it's 7am now).

My fusion drive is not split, if I go to disk utilities in recovery mode, there I can see Mac HD and Mac HD - data, but in OS, there it shows as one drive.

There is a chance, the SSD has gone berserk exactly at the time when I did the update to .2, but that's like 1: 1 000 000 000. If that's the problem, well... Time to pull the disk from the computer and change some parts.

Wish me luck.

Regards

-Mika

In you case - the Norton AV Software or for that matter, any AV Software from any Vendor is premised on the assumption that Viruses exist that affect macOS. There are no known Viruses in the wild that self replicate and affect macOS. There are Malware and Adware that does affect macOS and are often times downloaded as part of an Application from Third Party UnTrusted Site and get installed along with the Application. And for that ( Malware / Adware >>>Suggest downloading from a Trusted Developer and Respected ASC Contributor the application Malwarebytes for Mac. It is free or paid for added features. Run the Application and it should remove the malware / adware. Once done, restart computer and test.

What the Norton people have done is - polite words - is to re-infect the computer with software that is well documented on these ASC Forums as one of the worst, invasive and intrusive software that may have corrupted the OS to the point it may or may not require a Wipe and Reinstallation of the entire OS.

Why don’t you download MDS and use it to download 11.5.2 full installer, or download full installer from Mac App Store, , th3 install i5 on top of your 11.5.1

That is a personal choice. Though, the majority of users do not have such issues. At least, you will not generally find people without problems on these ASC Forums.