MemTest86 Locks Up

I have an ASRock X370 board with an AMD 3700X CPU. I've been running 16 GB of Corsair Vengeance, Samsung B-Die RAM at 3600 MT/s for months with no issues. MemTest86 will run for hours without errors or lockups, and the PC runs flawlessly.

I recently obtained a 32 GB Corsair Vengeance RAM kit, but this one uses Hynix AFR RAM at 3200 MT/s. Using XMP settings, or even stock 2133 settings, sometimes MemTest won't even start, and if it does, it freezes randomly, somewhere during the first pass. I even tried increasing the voltage, but that did not help.

Any ideas, anyone?