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.
server/src/internalClusterTest/java/org/elasticsearch/snapshots/ConcurrentSnapshotsIT.java
internalCluster().stopCurrentMasterNode();
        ensureStableCluster(3);
        awaitNoMoreRunningOperations();
        expectThrows(ElasticsearchException.class, snapshotThree::actionGet);
        expectThrows(ElasticsearchException.class, snapshotFour::actionGet);
        assertAcked(deleteFuture.get());
        try {
            createBlockedSnapshot.actionGet();
        } catch (ElasticsearchException ex) {
            
            
        }
    }
    public void testMultipleSnapshotsQueuedAfterDelete() throws Exception {
        final String masterNode = internalCluster().startMasterOnlyNode();
        internalCluster().startDataOnlyNode();
        final String repoName = "test-repo";
        createRepository(repoName, "mock");
        createIndexWithContent("index-one");
        createNSnapshots(repoName, randomIntBetween(1, 5));
        final ActionFuture<AcknowledgedResponse> deleteFuture = startAndBlockOnDeleteSnapshot(repoName, "*");
        final ActionFuture<CreateSnapshotResponse> snapshotThree = startFullSnapshot(repoName, "snapshot-three");
        final ActionFuture<CreateSnapshotResponse> snapshotFour = startFullSnapshot(repoName, "snapshot-four");
        unblockNode(repoName, masterNode);
        assertSuccessful(snapshotThree);
        assertSuccessful(snapshotFour);
        assertAcked(deleteFuture.get());
    }
    public void testMultiplePartialSnapshotsQueuedAfterDelete() throws Exception {
        final String masterNode = internalCluster().startMasterOnlyNode();