Only force shut down works

[SE-H]

An elderly friend has a 2010 iMac 21.5" working on High Sierra. Lots ofRAM and 1Tb SSD

Recently he had had huge problems accessing folders and other data. It turns out that, for months, he has not been able to shut down properly and can only do so with forced shut down i.e. power on button held until it crashes.

Using Target Disk Mode (as the optical drive could not be opened as the system seems to see it as a 'folder') we have taken all the data off onto the master machine, reformatted the SSD and reinstalled High Sierra.

Everything seems to be okay again, but the iMac will still not shut down normally, only with a forced shut down.

Given that an entirely new operating system has been installed into a formatted drive and there appear to no issues iwth the drive after testing with Techtool Pro and Disk Utility, does anyone have experience of this issue or any suggestions?

Many thanks.

PS, Its a long time since I started with a Mac back in 1988, but my 'expert' status expired on the introduction of OSx so any help will be much appreciated,

 

[TwoH]

Sounds to me like a software issue - possibly some program stopping the machine from shutting down wilfully?

 

[boswald]

You could check Activity Monitor to see what’s running before shutdown, I suppose. That’s what I’d do, and I’m no expert.

 

[now i see it]

iTunes on my Mac always hangs and won't quit. I have to force quit it every time. If I don't force quit it, the computer won't shut down.

Try this: Manualy quit (or force quit if necessary) all apps before attempting to shut down

 

[Fishrrman]

I agree with now I see it above.

Have him manually close all documents and then quit all running apps.
Then try the shut down.

If the iMac STILL REFUSES to shut down, I'd suggest using the "press the power on button in until it shuts down" trick.

Then, see if it will boot back up normally.
After the reboot, do things look ok?

This could be a software app or process that refuses to shut down, or it could be something else. It might be a "process" running in the background that's invisible to the user (that won't quit when the OS tells it to quit during shutdown -- hence, no shutdown).

Another thought:
Download and run the FREE version of MalwareBytes.
Does that find anything?

I'm wondering if it could also be a HARDWARE problem, perhaps in the iMac's power supply. If so, not worth fixing, considering the age.

If it was MY iMac, and it wouldn't shut down, I'd do this:
- shut down with the "power button push"
and then
- reboot next day
and then
- so long as it just keeps rebooting and running ok...
... I would use it "as it is".

Mac OS X is very "resilient". It can easily survive power outages with no detrimental effect to the OS.
This is why, in lieu of a repair that might be expensive on a 10-year-old iMac, I would just "press the button" and not worry about it...

(but I would keep a bootable backup in any case, use CarbonCopyCloner or SuperDuper to make one)