Nealx01yea thats a valid concern.. its a bummer you dont have another set of ddr4 that you can toss in to see if the issues persist. i have a 9900k.. 9900KS z390dark and the exact same memory kit your using here. i would offer to throw them all onto my testbench but im not sure it will do much to help. you said you had that kit running at XMP since around xmas time. so we know the dark CAN run those memory ICs.. just that there is some issue with your specific parts. so me trying to reproduce an issue might not be of any help. maybe try to track down a friend with some ddr4 you can borrow for a day or 2 or even better test your kit on their system if possible. if you can run stress tests for as long as possible to see if you can get any irregularities. if your kit is at fault Micron has amazing support for waranty and RMAs also. i just had a faulty SSD replaced and it came today by coincidence. process was extremely consumer friendly. no hoops to jump thru and no silly policies let me know if you would like me to throw all the same parts you have together and see what my results are. i might be able to do it tmro if you can get back to me quick enough.other thought, did you possibly move switch the bios by accident? probably not, but something to check in case you overlooked it.