The resharding_test_fixture.js configures multiple failpoints including "reshardingPauseCoordinatorBeforeCompletion" during setup only on the primary in the initial topology state. resharding_nonblocking_coordinator_rebuild.js is one test which enables elections which also enable them for config server in addition to shard replica sets. 

It is possible for the config server to have a change in primary during the execution of test and the new server won't have the failpoints configured causing the ReshardingCoordinator to return without blocking. Any tests dependent on the behavior of the reshardingPauseCoordinatorBeforeCompletion failpoint configured by the ReshardingTest fixture can potentially surface this issue.