emac_reset / EMAC_SW_RST not working

[pctj101]

esp-idf v3.3

My custom ESP32 board uses a LAN8720.
Over the past year I had many of them fail, so I'm trying to determine the root cause (I already have 50Mhz clock start delay and TVS ESD protection).

In esp_err_t emac_reset(void)

It calls
REG_SET_BIT(EMAC_DMABUSMODE_REG, EMAC_SW_RST)

However one of my boards always fails to reset this value back to zero0 (can't EMAC_SW_RST.

This of course means that any ethernet LAN8720 init will terminate prematurely leading to no MAC/no PHY.

Any particular hardware/software thing I can look into?