Slow performance and crashes after latest macOS 15.7.1 update on iMac

Please tell me someone else is getting this trouble?

I updated about 1 hour ago and since the restart I have had nothing but trouble.

I am running 15.7.1 (24G231) on my Retina 5K, 27-inch, 2019 iMac.

The issues are slow and disappearing mouse, Finder hanging, Apps hanging, I got one Screen of Death (or whatever it's called in macOS), and basically many apps are slow and hard to use due to lags.


This is crazy. What can I do to get this working? It's my work computer and I have jobs to get done tomorrow. Can't have crashes, lag and hanging apps.


Thanks in advance


Rob



[Re-Titled by Moderator]

Original Title: Latest Update - What happened!

iMac 27″, macOS 15.7

Posted on Oct 1, 2025 9:23 AM

Reply
Question marked as Top-ranking reply

Posted on Oct 2, 2025 2:11 AM

Part 1 of 2

Restart in Safe Mode. This will perform a Disk Repair, clear cache files and only load Apple Software, extensions and fonts. The boot up will be slow and can take some time - Normal.


Safe Mode will also eliminate Third Party Software, extensions and drivers from loading. It will only load the Minimum amount of Core Apple Processes to allow the the computer to function at a reduced Level of Performance 


Does the issue present in this mode ?


Sometimes a Safe Boot followed by a Normal Boot will just put things right.


If not - there could be something in the main User Account playing up. To further isolate this - Set up users, guests, and groups on Mac. Then log out of the Main User account and log into the dummy account and test again if the issue persists.


If the issue is present in the dummy account - then, this appears to be a System Wide issue on the computer.


Part 2 of 2


To Drill Down further and to avoid a session of Q&A, Q&A  and Q&A  


Download the Application Etrecheck  ( External Link ) directly from the Developer.


The Application is Not a " Silver Bullet "  and is  only a tool to examine the Hardware / Software used on this computer 


This is a Diagnostic Tool that makes no changes to the computer Hardware / Software used on this computer 


The application is free or paid from added features. 


The Report will Not Reveal Any Personal Information. 


Post back the Full Report - copy and paste - >>>> using the Additional Text Icon ( 3rd Icon to last ) <<<<

7 replies
Question marked as Top-ranking reply

Oct 2, 2025 2:11 AM in response to Rob Snow

Part 1 of 2

Restart in Safe Mode. This will perform a Disk Repair, clear cache files and only load Apple Software, extensions and fonts. The boot up will be slow and can take some time - Normal.


Safe Mode will also eliminate Third Party Software, extensions and drivers from loading. It will only load the Minimum amount of Core Apple Processes to allow the the computer to function at a reduced Level of Performance 


Does the issue present in this mode ?


Sometimes a Safe Boot followed by a Normal Boot will just put things right.


If not - there could be something in the main User Account playing up. To further isolate this - Set up users, guests, and groups on Mac. Then log out of the Main User account and log into the dummy account and test again if the issue persists.


If the issue is present in the dummy account - then, this appears to be a System Wide issue on the computer.


Part 2 of 2


To Drill Down further and to avoid a session of Q&A, Q&A  and Q&A  


Download the Application Etrecheck  ( External Link ) directly from the Developer.


The Application is Not a " Silver Bullet "  and is  only a tool to examine the Hardware / Software used on this computer 


This is a Diagnostic Tool that makes no changes to the computer Hardware / Software used on this computer 


The application is free or paid from added features. 


The Report will Not Reveal Any Personal Information. 


Post back the Full Report - copy and paste - >>>> using the Additional Text Icon ( 3rd Icon to last ) <<<<

Oct 3, 2025 2:59 AM in response to Owl-53

It hasn't happened over the past 2 days, and I did a series of app updates that had system extensions, so I am assuming that one of these caused the issue an dit's fixed with the updates. I will monitor if it happens again. Thanks for the previous help. IF it does happen again I will share EtreCheck details as I already have it one my computer.

Oct 3, 2025 1:22 AM in response to Rob Snow

Rob Snow wrote:

One thing I have noticed is that I am getting a slowdown only first thing in the morning since the update, and the I checked and I have like a 110GB cache total on my computer, and After Effects keeps adding this temp file of 100GBs even when I don't use it.

So what has come from the previous suggestions ?

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Slow performance and crashes after latest macOS 15.7.1 update on iMac

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