Help Understanding Crash Log - Crashes keep cycling into multiple crashes

For reference: If your Mac restarts and a message appears - Apple Support

• Some KP events suggest a specific cause. Unfortunately this is not one of those cases. A CPU failed to respond to a non-maskable interrupt in a timely manner... an arcane detail that is not helpful toward fixing it.
• Most KP events are caused by defective hardware, and in some cases by third party (non-Apple) drivers for that hardware. If you have anything connected to that Mac externally, try disconnecting it and determine if the KP events persist or subside. Unfortunately the only hardware that may be faulty appears to be its internal Wi-Fi hardware. That will require a trip to the Genius Bar.

You can try reinstalling macOS but I do not believe it will help. Try it anyway, then contact Apple to have that Mac evaluated for repair.

How to reinstall macOS - Apple Support

Official Apple Support

Have you tried running the Apple Diagnostics to see if it detects any hardware issues?

from Kernel Panic log:

Kernel Extensions in backtrace:

com.apple.driver.AppleAHCIPort

Hard to say if this could indicate a possible internal drive failure. I know some hard drive failures can cause the system to freeze up completely. It would not surprise me that a Hard Drive would be failing on a 2012 or 2013 iMac.

Phinx1 wrote:

I've got Finder to work sporadically now and it is fine until I access certain folders. I ran First Aid on both the data partition and the OS partition and no alerts resulted.

Run First Aid on the hidden Container. When First Aid is run on the hidden Container, it examines the container's file system, then it examines each of the APFS volumes within that container as well. Unfortunately Disk Utility hides the Container by default so within Disk Utility you need to click "View" and select "Show All Devices" before the hidden Container & physical drives appear on the left pane of Disk Utility.

Even if the First Aid summary says everything is "Ok", click "Show Details" and scroll back through the report to see if any unfixed errors are listed. If there are any errors (or "warnings"), then run First Aid again until they are gone. If after several scans the errors remain, then you need to run First Aid while booted from Recovery Mode. FYI, there are two warnings you can ignore....one a warning that a newer version of Disk Utility is being used (or APFS) and the other is something about "ignoring overallocation".

So it remains a bit unclear what exactly the problem is. I am wondering if it's a motherboard issue since I'm getting both the Finder crashes and WiFi not working. Will pursue more diagnostic efforts with your and the other responders thoughtful suggestions. Thanks!

A failing Hard Drive can potentially affect WiFi. I know when macOS is running slow, it can affect the WiFi details being reported.

If you can boot macOS normally or into Safe Mode, then run DriveDx (free trial period) to check the health of the drive(s). Post the complete DriveDx text reports for each internal drive here using the "Additional Text" icon which looks like a piece of paper on the forum editing toolbar.

If you cannot boot macOS to run DriveDx, then I can provide instructions for creating & using a special Linux USB boot disk to check the health of the internal drive(s).....plus it may reveal more details about what may be wrong with the system. Or if it boots & works fine, then it has been narrowed down to most likely being a problem with the internal drive....whether a failing drive, a file system issue, or a software issue. Just let me know if interested if you are unable to boot macOS to run DriveDx. Another option is to install macOS to an external USB3 drive & try booting the iMac from the external drive. We can gather a lot of useful information that way as well.

Concur, although not for it being faulty Wifi.

Given the presence of AHCI in the backtrace, I'd suspect the NMI was related to a page fault and attempt to access data from disk, and either the logic board disk controller, the SATA cable or the on-disk controller is bad.

Hardware diagnostics seem to be in order.