show fabric errors >> see if there are kind of errors.
show fabric channel-counters >> see if there are kind of errors.
sho fabric fpoe map >> To see which line card is mapped to channel 3.
If you see errors from show fabric error and channel-counters and it maps to the slot number on fpoe map. Suggestion is to re-seat that line card, it might not be seated properly or the line card channel is stuck hence losing sync with the fabric. Once the card is reseated please check "sh diag all" for any failures.
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