This read-only Counter32 counts blocks received on the Link interface that FEC was unable to correct, meaning those blocks were delivered with residual errors. Because this is the counter that actually reflects uncorrected transmission damage, an admin treats any nonzero, rising value here as a real service-affecting problem rather than a masked one. For example, if wvlinkNotCorrectedErroredBlocks starts incrementing after sitting at zero for weeks, that signals the fade margin has been exceeded and FEC can no longer fully compensate, warranting an on-site antenna check.