This is a Counter-typed running total of corrupted V.54 test messages received through the newer consolidated loopback mechanism, the counterpart to cdx6500NMV54BadMsgsReceived. A nonzero and climbing value here during an active loopback is the direct evidence of line-quality problems on whichever port is currently under test via this mechanism. For example, if this counter climbs steadily while the sent-message counter also climbs, the circuit is failing consistently rather than intermittently.