Today if we detect concurrent modification of a snapshot repository then we mark it with `CORRUPTED_REPO_GEN` which blocks further writes to try and prevent additional damage to its contents. You can remove the marker by calling the register-repository API again, but this API will discard no-op re-registrations without taking any action. You can work around this by unregistering the repository first (which may be impossible if it's still in use for searchable snapshots) or by re-registering it with some trivial setting change (which seems hacky).

We should not consider it a no-op re-registration if the repository is currently marked with `CORRUPTED_REPO_GEN`, because doing this re-registration will re-read the repo contents and clear the corruption marker and therefore is not a no-op.
test/framework/src/main/java/org/elasticsearch/snapshots/AbstractSnapshotIntegTestCase.java
) {
        logger.info("--> creating full snapshot [{}] to repo [{}]", snapshotName, repoName);
        return clusterAdmin().prepareCreateSnapshot(repoName, snapshotName).setWaitForCompletion(true).setPartial(partial).execute();
    }
    protected void awaitNumberOfSnapshotsInProgress(int count) throws Exception {
        logger.info("--> wait for [{}] snapshots to show up in the cluster state", count);
        awaitClusterState(state -> state.custom(SnapshotsInProgress.TYPE, SnapshotsInProgress.EMPTY).count() == count);
    }
    public static void awaitNumberOfSnapshotsInProgress(Logger logger, int count) throws Exception {
        logger.info("--> wait for [{}] snapshots to show up in the cluster state", count);
        awaitClusterState(logger, state -> state.custom(SnapshotsInProgress.TYPE, SnapshotsInProgress.EMPTY).count() == count);
    }
    protected SnapshotInfo assertSuccessful(ActionFuture<CreateSnapshotResponse> future) throws Exception {
        return assertSuccessful(logger, future);
    }
    public static SnapshotInfo assertSuccessful(Logger logger, ActionFuture<CreateSnapshotResponse> future) throws Exception {
        logger.info("--> wait for snapshot to finish");
        final SnapshotInfo snapshotInfo = future.get().getSnapshotInfo();
        assertThat(snapshotInfo.state(), is(SnapshotState.SUCCESS));
        return snapshotInfo;
    }
    public static final Settings SINGLE_SHARD_NO_REPLICA = indexSettingsNoReplicas(1).build();
    protected void createIndexWithContent(String indexName) {
        createIndexWithContent(indexName, SINGLE_SHARD_NO_REPLICA);
    }
    protected void createIndexWithContent(String indexName, Settings indexSettings) {
        logger.info("--> creating index [{}]", indexName);
        createIndex(indexName, indexSettings);
        ensureGreen(indexName);
        indexDoc(indexName, "some_id", "foo", "bar");