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/main/java/org/elasticsearch/repositories/RepositoriesService.java
throw newRepositoryConflictException(repository, "snapshot is in progress");
        }
        for (SnapshotDeletionsInProgress.Entry entry : clusterState.custom(
            SnapshotDeletionsInProgress.TYPE,
            SnapshotDeletionsInProgress.EMPTY
        ).getEntries()) {
            if (entry.repository().equals(repository)) {
                throw newRepositoryConflictException(repository, "snapshot deletion is in progress");
            }
        }
        for (RepositoryCleanupInProgress.Entry entry : clusterState.custom(
            RepositoryCleanupInProgress.TYPE,
            RepositoryCleanupInProgress.EMPTY
        ).entries()) {
            if (entry.repository().equals(repository)) {
                throw newRepositoryConflictException(repository, "repository clean up is in progress");
            }
        }
        for (RestoreInProgress.Entry entry : clusterState.custom(RestoreInProgress.TYPE, RestoreInProgress.EMPTY)) {
            if (repository.equals(entry.snapshot().getRepository())) {
                throw newRepositoryConflictException(repository, "snapshot restore is in progress");
            }
        }
    }
    private static void ensureNoSearchableSnapshotsIndicesInUse(ClusterState clusterState, RepositoryMetadata repositoryMetadata) {
        long count = 0L;
        List<Index> indices = null;
        for (IndexMetadata indexMetadata : clusterState.metadata()) {
            if (indexSettingsMatchRepositoryMetadata(indexMetadata, repositoryMetadata)) {
                if (indices == null) {