This field reports the number of packets received with CRC errors by this PM instance, exposed here as cienaCesPmExtendedTxRxStatsBinRxCrcErrorPkts. On this Ciena CES port's PM data, a CRC/FCS mismatch means the frame's checksum didn't match its contents by the time it reached this port's MAC, which is a physical-layer signal-integrity symptom — bad cable, dirty connector, marginal optic, or a failing NIC on the far end — not a software or config issue; and this sits in the currently active extended Tx/Rx interval bin — its sibling StartTime/ClearTime fields mark exactly which window is being counted, so a change here reflects activity happening in the live collection interval, not something already filed away in history. For example, a healthy port would sit at 0 for CRC-error frames in this bin; even 1 is enough to warrant a look, since this class of counter isn't supposed to move under normal operation.