would someone look at my crash log please?

See if there are any other Kernel Panic logs in "/Library/Logs/DiagnosticReports" and the "Retired" subfolder. Kernel logs usually have file names containing "kernel" and/or "panic". It is odd that the EtreCheck report did not show the posted Kernel Panic log, but I don't know if it checks the Retired subfolder.

Make sure you completely exit any game apps since they tend to do some odd things to the system behavior and one of them could be holding onto something related to the GPU when you are trying to shutdown the system.

Here is a link to the DriveDx app:

https://binaryfruit.com/drivedx

Post the complete DriveDx text report here using the "Additional Text" icon which looks like a piece of paper on the forum editing toolbar.

I doubt your 2015 iMac hardware is supported by Apple anymore, so you may just want to put the iMac to sleep instead of powering it off.

You have enough Free storage space on your Fusion Drive that you can create a new APFS volume and install a clean copy of macOS onto the new APFS volume to test if the clean install has the same issue. Just make sure to test the clean install without installing any third party apps and before restoring from a backup (assuming you have a backup). If you have problems with a clean install under these conditions, then it means you either have a file system issue (we didn't erase the drive for a true clean install), or some sort of hardware issue. Installing macOS onto another new APFS volume will keep your current macOS installation intact and it is very easy to just delete the new APFS volume after you are done testing (boot back into the main system first). If there are no issues, then I would suggest trying to install & play your game(s) on the new macOS installation to see if it has any issues.

Did anything recently change with your system hardware or software? Even a minor software or OS update?

I would also disconnect all external devices from the computer just in case one of them is causing a problem.

You can try running the Apple Diagnostics, but I doubt it will detect any issues, but it never hurts to try.

It never hurts to perform an SMC Reset and PRAM Reset (hold the PRAM Reset for at least three chimes if possible).

No clear culprit.

The Fusion drive might be failing. A failing Fusion tends to cause flaky issues elsewhere. DriveDx can potentially see further into that storage.

Another possible cause of these errors is external USB hardware and cabling. I’d remove all that, restart, test, and see if issues persist.

The Epic Games app is failing (either removed incorrectly, or it has a bug), and I’d delete that plist, and would check with Epic about bugs or issues or updates or removal instructions.

I’d check for updates for installed apps including the audio plugins, or remove those if not in use.

Or this is failing hardware.

This iMac seems to be decidedly lacking in backups. I’ll assume that means the user data here has no value.

ninthname wrote:

thanks for the guidance, i really appreciate it.

in case you're interested, i haven't used the epic games app in some time. i do have a usb strip as an iMac with only three USB ports in this day and age is criminal (looks like they haven't improved much on that end), and as i said i am headed to acquire a new one next week so hardware issues wont be a concern.

Apple is pushing wireless services hard, whether that’s Bluetooth for comms and audio, or a wireless- or wired-connected NAS serving Time Machine, or otherwise.

And Apple has (finally!) started offering higher-end Ethernet, where faster connections are needed/

And in most vendors’ product lines, lower-end gear has fewer ports than higher-end gear. The Apple gear does have seriously fast ports, though. That iMac 5K 2015 has two Thunderbolt 2 ports — those ports are basically PCIe buses — with up to 20 Gbps transfer speeds, which was quite good in 2015. Newer Mac ports are yet faster.

i am not sure what to make of your highly stoic remark about backups. my time machine says backups are occurring and intact, last one today at 1:43, and i have a second BUD i use monthly. perhaps at the time of this crash there was some problem with backups i don't remember.

You’re backing up to local storage using Snapshots, per what is shown. That is the same storage on the same device that can fail, get dunked, get dropped, get lost, get stolen, or get corrupted.

Post the Etrecheck data, please.

iMac 27” 5K late 2015.