This counts frames received over the satellite interface that failed the HDLC-level CRC integrity check. This is the most direct indicator of raw RF link quality on the satellite path, since errors here mean bits were corrupted in transit before any higher-layer packet processing even occurs, distinct from the separate packet-processor CRC errors tracked elsewhere. For example, a steady baseline of a few CRC errors per day with an occasional spike to hundreds during a signal-fade event is a normal satellite-link fingerprint worth tracking.