The article explains about the following log messages

Mar 20 17:00:01 router fpcx-kernel: ixgbe 0000:84:00.0: Warning firmware error detected FWSM: 0x0028801A

Mar 20 17:00:01 router fpcx-kernel: ixgbe 0000:84:00.1: Warning firmware error detected FWSM: 0x0028801A

Mar 20 17:00:03 router fpcx-kernel: ixgbe 0000:84:00.0: Warning firmware error detected FWSM: 0x0028801A

No traffic impact, however, can notice the log messages in the syslog file.

- These logs from ixgbe kernel driver indicate 10G NIC X552 device firmware error in the fpc. 
- The value printed in the log is from FWSM(Firmware Semaphore - 0x00010148) register. Value in bits[24:19] - 0x05 indicate firmware error "Shadow RAM dump fault"
- Bit 15(FW_VAL_BIT) in FWSM register is set indicating firmware is valid and the error logged is not a fatal error. 
- FPC coming up online and functioning indicate no problems with RE-FPC communication.

Please collect the following outputs from the FPC which is logging the above messages and from another FPC as well.

start shell user root

vssh fpcx <<<< FPC reporting the logs

ethtool -i eth0

ethtool -i eth1

exit

vssh fpcy <<<< FPC not reporting the logs

ethtool -i eth0

ethtool -i eth1

exit

Generally reboot will clear the logs, if not please reach out to JTAC with the outputs collected from the above commands, pre and post reboot.