How to resolve freezing and crashing issues on iMac running macOS 15.7.9?

The EtreCheck report actually points pretty strongly to the internal HDD/APFS I/O path rather than a bad container layout. Your 1 TB 5400-RPM disk is only managing about 54 MB/s reads and 47 MB/s writes, while apfsd is repeatedly consuming ~86% CPU, which is a big clue that the system is spending excessive time servicing APFS filesystem work on a very slow mechanical device.... APFS is particularly unforgiving of random I/O and metadata-heavy workloads, so once macOS starts doing filesystem housekeeping, snapshots, indexing, VM activity, or other concurrent I/O, the whole UI can appear to freeze because processes are waiting on storage, not because Finder itself has crashed.

The fact that booting Sequoia from an external SSD makes the machine usable is an important diagnostic result and makes the internal drive the first thing I would suspect. I would leave the existing APFS container and its system/data/preboot/recovery/VM volumes alone and use the external SSD as the startup disk... if you want to confirm the diagnosis, compare the machine's behaviour while the internal disk is largely idle versus when it is being accessed, and check the internal drive's SMART/health and system logs for I/O errors or APFS-related messages.

If the external SSD remains stable while the internal HDD produces beachballs, high apfsd activity or I/O errors, replacing the internal HDD with an SSD is the real fix, not deleting APFS volumes.

You're welcome.

Those Disk Images are not causing your Freezing or Crashing issues and can be Deleted.

To look into and sort out why your iMac is Freezing and Crashing...

Download and run the free version of EtreCheckPro, from > https://etrecheck.com/en/index.html

Then post back here with your Report, as per > How to use the Add Text Feature When Post… - Apple Community

Sadly that 2019 21.5" base-model iMac's has a slow 1T 5400rpm HDD that is now showing signs of failure.

What you can do to get some more life out of that iMac, is run it from an external SSD.

see > Use an external SSD as your startup disk … - Apple Community

The Disk Utility sidebar information for your Internal disk looks normal.

To expand the sidebar grab the divider and drag it slightly to the right.

To see the amount of used drive space select the Container disk instead of the drive.

As for the Disk Images in your screenshot..?

You need to highlight each one of those and provide a screenshot for each one.



kennethfromgrange wrote:

I have downloaded Mac OS Sequoia to my external HD and have been working from that.

Good work.

Do I now need to delete any disks from Disk Utility if so could you tell me which ones.

No, there is no need to delete or change anything.

Thank you.

You’re welcome!

thank you for taking the time to help me

thank you for your help

I have downloaded Mac OS Sequoia to my external HD and have been working from that. Do I now need to delete any disks from Disk Utility if so could you tell me which ones. Thankyou