All I can say is that some cpus don't like certain timings on ram. I have an 8700k that will do mem at 4400 17-17-17-34, but if I set those same sticks to 4200 with same timing it boot loops at post code 7f. Same boot loops at 4400 if I try to get rtl's closer to the same on both channels. Like channel a is set at 67 but channel b is 70 or 71, I can't remember exactly. It's also very weird with ram at default jedec speeds and trying to set primary timings very loose to see what kind of frequencies the ram can do.
That 8700k will either boot loop or train on first try, no in-between.