1769-L2x and 1769-L3x, L4x controllers need to be flashed to v19.015 or v20.013. (This anomaly doesnt exist in those firmware versions )
CompactLogix 5370 L2 and L3 controllers need to be flashed to v20.014 or higher within major revision 20 or v21.011 or higher.
1769-SDN needs to be flashed to v4.004.
Flashing should only be done via Ethernet backplane if the controller version is V21 or higher. Otherwise need to flash via DeviceNet using 1784-U2DN module or similar device.