Guess I spoke too soon. Although at 3733 MT/s my setup passes overnight runs of OCCT and MemTestPro, it doesn't last more than an hour in game before it locks up and reboots. I've spent an entire day now trying to fix it, including loosening pretty much every timing, raising and lowering VDDP between 0.9 and 1.0 V, raising CLDO_VDDP to 1.0 V, raising CLDO_VDDG to 1.0 V, lowering and raising VDIMM between 1.35 and 1.45 V, lowering procODT to 40 Ohms, and even lowering the speed to 3666 MT/s while keeping the same timings. Nothing fixes it.
Not sure what else I can try at this point and I don't even have a reliable way of knowing it's stable except "keep playing non-competitive matches until it crashes".
Aaaaaaaand now it's crashing at my "stable" 3200 MT/s profile too. Maybe my CPU is dying. Or maybe my GPU.