This Counter32 (frames) counts frames dropped by the OAM multiplexer due to transmit resource contention, per its description, since the multiplexer combines OAM PDUs with normal traffic onto a single output and can drop frames when that output is momentarily oversubscribed. This is specifically a resource-contention counter, not a link-quality or error counter, so an incrementing value points to the local device's internal OAM frame-handling capacity being exceeded rather than anything wrong with the link itself. An engineer seeing dropped user frames alongside a rising value here would suspect OAM multiplexing overhead is contributing to loss on a heavily loaded port, rather than blaming the physical link.