This counts UDP test frames received with a bad UDP checksum, which is a data-corruption indicator distinct from loss, duplication, or reordering, since these frames physically arrived but their contents were altered somewhere in the path. An admin flags a nonzero value here as evidence of a hardware or cabling fault (like electrical noise or a failing transceiver) corrupting payload bits, rather than a congestion or queuing problem. For example, a steady trickle of checksum errors that scales with test rate but not with port utilization would point the operator toward a marginal optic or a bad patch cable rather than a switching-capacity issue.