I have the same problem and error code on my network of 7 PLC's.  They all have CP343-1 Lean cards on them and sharing comms between them.  It has been working fine for years and all of a sudden the one CP card starting giving problems then that cleared and the fault moved to another CP card.  The comms still work but every every 2 minutes or so the comms drop for about 30 seconds and then resume.  It is not one the same connection partner in the error code but all the connection partners.

Any assistance would be greatly appreciated.

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Split from Clearing BF error on CP-343-1 Lean.