Constant Kernel Panics (after system goes to sleep?) since booting up from power failure

A power outage or surge could have damaged the power supply or perhaps even the Logic Board. If you are using a surge power strip, then try plugging the iMac directly into the wall electrical socket instead just in case the power surge strip sustained damage from a surge.

It is most likely a memory problem since the Kernel Panic log snippet in the report references "memcpy" which is "memory copy" and the size check failed. The first suspect would be the memory from the upgrade since Macs are very picky about the memory used. What is the make & model of the memory used for the upgrade?

You can try running the Apple Diagnostics to see if any hardware issues are detected.

You can also try running Memtest86 to see if any issues show up with the memory. If the default settings don't reveal a problem, then change the Memtest86 CPU options to "Round Robin" and "Sequential" to see whether the tests have any problems when using either CPU option. I have been finding that these Memtest86 CPU settings tend to cause the memory test to freeze fairly quickly if there is a hardware issue...this is just as useful as an actual error result because it means you can remove memory modules to see if the issue is resolved.

I would modify the Memtest86 CPU options as described since I haven't been getting many errors using the defaults, but have had the memory test freeze up regularly usually within a short period of time indicating a hardware issue of some sort (usually memory).

With the larger faster memory, the other timings are a bit slower than the factory ones. Crucial doesn't mention anything about issues mixing the original & upgraded modules, but you may want to remove the Apple modules to see what happens.

https://www.crucial.com/compatible-upgrade-for/apple/imac-(retina-5k--27-inch-3*4ghz-intel-core-i5--2017)-imac18-3

I would first run Memtest86 with the custom CPU options "Round Robin" and "Sequential" first just so you have a baseline on how things are working with the current configuration. Running the tests again after removing the Apple original modules to compare may give you some quick insight (or running the test with just the original Apple memory). This is what I would do in order to understand if I have a bad module or just a compatibility issue.

Try booting into Safe Mode and see if it panics after wake from sleep.

If it still panics, it may be a hardware fault.

If it doesn't panic, it is likely one of the many kernel extensions you have installed.

I don't know how any of your kernel extensions would interact with Chrome, but if you can make some connection, that might help rule out some of them.

With a power surge, I would suspect some sort of hardware problem, most likely with an external device, but you seem to have rule those out. Do you have an additional monitor?

If you have a panic log, there is a section named "loaded kexts." If there are third-party kernel extensions listed there, they may be the cause.

The report mentions a kernel panic that appears to have been associated with memory.

There is a possibility that one of the memory modules may have been affected.

Running Memtest86, as advised by HWTech, seems a good idea.

It has been a while since I created my last bootable Memtest86 USB stick. You should be able to use Etcher to create the bootable USB assuming you are able to use the entire USB stick. Use the downloaded Memtest86 .img file as a source for Etcher.

I believe I have also manually created & transferred the contents of the mounted Memtest86 .img file to a drive with GUID partition and used both FAT32 and even HFS+ volumes (they will just show up as orange icons with the "EFI" label when created this way). Creating it this way may not work on all Macs as I seem to recall (or maybe it only affect my ability to put a boot label on the volume when Option Booting).

robingo wrote:

I then ran Rembr overnight (I will still run Memtest86 but that requires a 512G USB flash drive and I didn't have a large enough one, so one is on order).

Memtest86 only takes about 10 MBs of space so any USB stick will have sufficient space. Not sure where you are getting 512GB from.