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
}
    /**
     * Unregisters repository in the cluster
     * <p>
     * This method can be only called on the master node. It removes repository information from cluster metadata.
     *
     * @param request  unregister repository request
     * @param listener unregister repository listener
     */
    public void unregisterRepository(final DeleteRepositoryRequest request, final ActionListener<AcknowledgedResponse> listener) {
        submitUnbatchedTask("delete_repository [" + request.name() + "]", new UnregisterRepositoryTask(request, listener) {
            @Override
            public void clusterStateProcessed(ClusterState oldState, ClusterState newState) {
                if (deletedRepositories.isEmpty() == false) {
                    logger.info("deleted repositories [{}]", deletedRepositories);
                }
            }
            @Override
            public boolean mustAck(DiscoveryNode discoveryNode) {
                
                return discoveryNode.isMasterNode() || discoveryNode.canContainData();
            }
        });
    }
    /**
     * Task class that extracts the 'execute' part of the functionality for unregistering
     * repositories.
     */
    public static class UnregisterRepositoryTask extends AckedClusterStateUpdateTask {
        protected final List<String> deletedRepositories = new ArrayList<>();