In case anybody else has this problem. In our case it was either a defective L01 OEM module or a manufacturing defect with the PCB. We built a second unit and the LoRa worked fine in that L01 module. It did not hang or crash, and the LoRa pings worked fine over several minutes of testing.

OEM modules use 1.8v flash and ram. not sure if they are powered by discrete ldo or esp32 onboard ldo and whether the pin is intended as alternate supply or output.