The BF-14549 failure happens when recipient shard fails to update its routing table once the moveChunk completes.
As such it issues a StaleConfig error on the attempt to insert instead of the expected MigrationConflict (https://github.com/mongodb/mongo/blob/v4.2/jstests/sharding/transactions_reject_writes_for_moved_chunks.js#L129)
The proposed fix is to either add the StaleConfig to the list of allowed errors as its expected behavior or make sure that the recipient routing table is updated before the insert.
In both cases it's a test case change.