Hello everyone,
I tested Danne's recent build from October 13th, found here:
https://www.magiclantern.fm/forum/index.php?topic=23041.msg216899#msg216899 I haven't encountered the artifacts at ISO 1600 with long takes. I used MLV App and tested 12 bit lossless and 14 bit lossless. Tested 3.5K and 1920x818 with frames per second at 23.976 and exact.
It was really hot out, and in order to test ISO 1600, I had to use a variable nd. I tried to reproduce the issue by shooting long takes out in the heat. The only issue I saw was vertical banding. Other than that there was some of lens flaring with the Canon 16-35 f2.8 Mark I.
I'll have to test more, but so far I haven't encountered the issues I was having before.
Also, before installing Danne's build, I uninstalled Magic Lantern (was using the July 22nd, 2018 Crop Rec 4K Experimental Build) by formatting both the SD and CF card. I used Sandisk Extreme Pros. I then used a card reader to copy the files from Danne's build to both memory cards. Then I updated the firmware, rebooted, and experienced a few issues with loading modules. There were errors. Fortunately I was able to get the modules working by loading mlv lite. I will provide a link when I get a chance of all the settings I used. I decided to restore ML settings to default, then changed settings from there. There were no error files on my SD card or CF card.
Thanks for all of your help. I'll continue testing, but so far, so good

- Paul