This read-only counter counts Join/Prune messages received from this neighbor that contained errors, specifically excluding cases where the RP address in the message differs from the locally known RP or where a (*,G) message was received for an SSM group. An admin can use this narrowed error count to catch genuinely malformed Join/Prune packets without being distracted by expected RP-mismatch or SSM edge cases. For example, a rising count here despite RP configuration being consistent across the domain would point to real packet corruption from that neighbor.