Remember 2933 is officially supported.
Had to tune these exact settings (every single one of these - one missing, and it falls apart):
CPU SOC Voltage: 1.200v
SOC Load Line Calibration: Level 4
SOC Current Capability: 130%
DRAM Voltage: 1.41v (droops down to ~1.368v in reality)
Gear Down Mode: Enabled
Power Down Mode: Disabled
MemCadBusClkDrvStren: 24.0 Ohm
MemCadBusAddrCmdDrvStren: 24.0 Ohm
MemCadBusCsOdtDrvStren: 24.0 Ohm
MemCadBusCkeDrvStren: 24.0 Ohm
It can be challenging to get 256gb memory working on Threadripper at an overclocked speed beyond 2933 – try these settings if XMP isn’t doing it and you have stability issues.