iMac: New RAM causing random shut down

Have you taken the RAM upgrades out and tested the computer without them? IF not, do so. I've purchased hundreds of RAM upgrades from OWC and I can think of two times I've gotten a bad upgrade from them. It happens, but OWC is good and fast about replacing bad RAM.

The thing about memory diagnostics is that marginal RAM can pass the test time after time. Unfortunately the only 100% positive test for bad RAM that I've come across is taking it out and seeing if the computer behaves without it.

RAM can be recognized and still be bad. In fact what you are describing is one of the things I have dreaded most as a tech - marginal RAM. I dreaded it because really marginal RAM needs to get warm first and can actually go days without hiccuping. That's why I recommended taking out the new chips. It is a fast first step to diagnosis. Take them out - if the computer works flawlessly then take out what you have and put just the new chips in the slots the original RAM was in. If the hiccups begin you know it was that RAM and not the slots you put them in.

Users have found that other sources like Amazon do not have the same quality modules as available directly from MacSales. I'd return then and get replacements directly from OWC.

Sorry you're having that problem. Where did you purchase your RAM? I've found that some RAM causes problems. Did you get directly from Apple?If not, that might be the problem. I suggest you download and run the free app EtreCheckPro. it often sees and reports problems. It makes no changes to your system and does not post any personal data. You can post the report here on the paperclip below and someone will look at it to see if anything needs to be done. Good luck.

I like to use this when I'm testing my RAM, it's a bit more thorough than what Apple does

https://www.memtest86.com (regardless of it's name it's 64 bit)

Ive ordered a bunch of OWC RAM in the past and I did have one issue but they were quick to send me replacements and take care of it.

Is the RAM spec as shown below?

Maximum Memory 16 GBMemory

Slots4 - 204-pin PC3-10600 (1333 MHz) DDR3 SO-DIMM

Do note it can be upgraded to 16GB.

I would remove the new modules and making sure there is no dust in the RAM slots. When we upgraded RAM in an older iMac whose RAM door had not been opened since new, we found the two unused slots were filthy. The Ram slots sit between two air intakes and catch a lot of lint.

Lib dwb I have bought all our Mac RAM from OWC for over 15 years and received one set that had issues that they walked me through.

I totally agree with dab. Having spent many years in the telecommunications industry, I learned that actions such as this are how we can prove where the problem lies. I wish I had thought to suggest this.

Although probably not related to RAM, you have several things that are known performance killers:

1) Because, like a cat, macOS cleans itself, all fearware like Clean My Mac are scams.

2) Although not loaded at time of the test, I see several components of another AV package, AVG. All bad.

3) This can indicate problems:

Configuration Files:
  /etc/hosts - Count: 20

Please see this User Tip for information on etc/hosts files and how to deal with them:

https://discussions.apple.com/docs/DOC-8091

That's a start. You have some other things I don't recognize but dealing with the above is a step forward to seeing better overall performance.