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
ClusterService clusterService,
        @SuppressWarnings("SameParameterValue") String source,
        ClusterStateUpdateTask task
    ) {
        clusterService.submitUnbatchedStateUpdateTask(source, task);
    }
    /**
     * Set the repository UUID in the named repository's {@link RepositoryMetadata} to match the UUID in its {@link RepositoryData},
     * which may involve a cluster state update.
     *
     * @param listener notified when the {@link RepositoryMetadata} is updated, possibly on this thread or possibly on the master service
     *                 thread
     */
    public static void updateRepositoryUuidInMetadata(
        ClusterService clusterService,
        final String repositoryName,
        RepositoryData repositoryData,
        ActionListener<Void> listener
    ) {
        final String repositoryUuid = repositoryData.getUuid();
        if (repositoryUuid.equals(RepositoryData.MISSING_UUID)) {
            listener.onResponse(null);
            return;
        }
        final RepositoriesMetadata currentReposMetadata = clusterService.state()
            .metadata()
            .custom(RepositoriesMetadata.TYPE, RepositoriesMetadata.EMPTY);
        final RepositoryMetadata repositoryMetadata = currentReposMetadata.repository(repositoryName);
        if (repositoryMetadata == null || repositoryMetadata.uuid().equals(repositoryUuid)) {
            listener.onResponse(null);