What are you using to stress?
OCCT will find most instabilities. The bad thing about this platform is programs rarely crash it's just a full hard system crash. If you are right on the edge of stability then these random crashes will occur. It is generally recommended that you find your max overclocks then back off a little.
I find it hard to believe there are so many duff motherboards around.
@eyetrip have you tried with 32gb of ram? Not saying any is faulty it just might not like pushing 64gb despite passing tests. Also when you say stutter, what kind of stutter?
Prime, realbench, tpu memtest
Fair point. Perhaps it's time to try OCCT and HCI...