1. A requests segment from B (there are multiple chunks)
2. B sends all chunks, but before A receives them, new topology arrives and A cancels the ST.
3. Another topology comes and A requests this segment again
4. A receives the old StateResponseCommand with lastChunk=true and thinks that it got all segments, therefore, it discards further chunks.

Result is inconsistent cluster, and after further rebalances completely lost data.
This ought to be rare, but was repeatedly observed when gracefully stopping coordinator on a 32-node cluster full of data.