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
for (String snapshot : Arrays.asList(snapshotOne, snapshotTwo)) {
            SnapshotInfo snapshotInfo = getSnapshot(repoName, snapshot);
            assertThat(snapshotInfo.state(), equalTo(SnapshotState.SUCCESS));
            assertThat(snapshotInfo.shardFailures().size(), equalTo(0));
        }
    }
    public void testBackToBackQueuedDeletes() throws Exception {
        final String masterName = internalCluster().startMasterOnlyNode();
        internalCluster().startDataOnlyNode();
        final String repoName = "test-repo";
        createRepository(repoName, "mock");
        createIndexWithContent("index-test");
        final List<String> snapshots = createNSnapshots(repoName, 2);
        final String snapshotOne = snapshots.get(0);
        final String snapshotTwo = snapshots.get(1);
        final ActionFuture<AcknowledgedResponse> deleteSnapshotOne = startAndBlockOnDeleteSnapshot(repoName, snapshotOne);
        final ActionFuture<AcknowledgedResponse> deleteSnapshotTwo = startDeleteSnapshot(repoName, snapshotTwo);
        awaitNDeletionsInProgress(2);
        unblockNode(repoName, masterName);
        assertAcked(deleteSnapshotOne.get());
        assertAcked(deleteSnapshotTwo.get());
        final RepositoryData repositoryData = getRepositoryData(repoName);
        assertThat(repositoryData.getSnapshotIds(), empty());
        
        assertThat(repositoryData.getGenId(), is(3L));
    }
    public void testQueuedOperationsAfterFinalizationFailure() throws Exception {
        internalCluster().startMasterOnlyNodes(3);
        internalCluster().startDataOnlyNode();
        final String repoName = "test-repo";