This is the event that occurs on ENET_RX_ER pin (P1.14), so if the PHY for some reason drove this pin high, it should (eventually) show up as a high SymbolError bit, and on Receive Status Vector bit 19. It's an indicator that the whole frame is suspect, and should be discarded. Basically, the PHY is indicating that there is an error raising the ENET_RX_ER line, and the user must investigate why the PHY is asserting this line