Have you selected the correct pins for your industrial application? ICSSG pins allow muxing at the ICSSG IP level and at the SoC level using the PADCONFx registers. Carefully check that you have connected your schematic correctly for your application. In particular, review the differences between the RGMII connections and the MII connections for the TX pins.
Are you using an MII interface to an Ethernet PHY? Some industrial protocols require the use of a 10/100-Mbit Ethernet. MII may be required to operate these protocols correctly. Check with your PHY manufacturer to determine if MII is needed.
Have you terminated your RGMII signals correctly? For the RGMII interfaces, 22-Ω series termination resistors must be placed on all 12 interface signals as close to the transmitter as possible.