This read-only counter records how many frames the physical unit's channel failed to reassemble because at least one block in the sequence was missing. It tells an administrator that data is being lost in transit at the block level, which is a more specific symptom than a generic abort and often points to buffer overruns or intermittent connectivity on that channel. For instance, a technician troubleshooting slow terminal response on a PU might check statPuChSeqErrs and find it climbing in step with user complaints, confirming that blocks are being dropped between the host and the unit.