computer froze while running memtest86

was running memtest86 yesterday, and it ran thru the first 3 passes with zero errors, but halfway thru the 4th pass it froze, while running the "moving blocks" test, It was still showing zero errors when it froze.

Memory is Corsair Vengence LPX DDR4, 2800, 64 GB total. Ram was purchased as matching sets of 4 sticks each (8 gb sticks) as i couldn't find full 64 GB matching sets.

Does it freezing say anything about the ram or the motherboard?

 
thanks, there also aren't any 8 stick matched sets offered on the market - these were on the QVL as 32 GB sets, so i bought 2 sets, 4 sticks each and hope they "played nice" with each other

memtest86 didn't allow me to select what speed to test at, and it identified the sticks as "2998 MHz" and if i understand the text displayed correctly, it was testing them at that speed

after posting here i remembered there was a forum specific to memtest86 over on passmark's website - went there and found more than a few folks with the same issue, memtest freezing during testing, in fact it was more than just a few - there's also a list, already started of motherboards with particular CPUs known to have this freezing issue and apparently the issue is somewhere in the mobo's BIOS. My board wasn't on that list though. It could still be a BIOS issue, But if not, according to that forum, it's either CPU, mobo or ram issue.

My next step is to test these sticks two at a time - running the full 4 pass test took 9+ hours so this is going to be a week or so testing in the evenings. If they all test good, i'm going to try just running this rig with only 32 gb of ram and leave 4 sticks out
 
when i first built, i only intended to run 32GB, and decided later to add 32 more
called into asrock and spoke to one of their techs, basically had me bump the ram speed up to 2800
but he confirmed what they're saying over on the memtest forum, there's a bug in most BIOSs that conflicts with whatever code memtest is running

after he had me bump it to 2800, i ran Prime95 for awhile, no crashes, or issues, so i'll leave it alone
if it re-occurs, i'll pull four sticks out