In the test, we are stopping replication on one secondary and then performing a write on the primary. We then wait for the write to be replicated to the second secondary. However, we are seeing that the secondary fails to replicate this change because its sync source is set as the other secondary whose replication has been paused. This can happen due to chained replication, as we saw in a similar test here. Disabling chaining will force the secondaries to replicate from the primary which should fix this issue.