I can also add that I cannot get them to cold boot at 3600-3800 MT/s with CAS 16. They run happily on CAS 16 if set in ryzen master and reboot, stable in memtest etc. Cold boot still no go.
Bumping CAS to 18 resolves cold boot problem. Don't know why it won't even cold boot at CAS 16, 3600 MT/s as stated in the specs. They perform well enough at 18-20-21-39.