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
}
            }
            Map<String, Repository> builder = new HashMap<>();
            
            for (RepositoryMetadata repositoryMetadata : newMetadata.repositories()) {
                Repository repository = survivors.get(repositoryMetadata.name());
                if (repository != null) {
                    
                    if (canUpdateInPlace(repositoryMetadata, repository) == false) {
                        
                        logger.debug("updating repository [{}]", repositoryMetadata.name());
                        closeRepository(repository);
                        archiveRepositoryStats(repository, state.version());
                        repository = null;
                        try {
                            repository = createRepository(
                                repositoryMetadata,
                                typesRegistry,
                                RepositoriesService::createUnknownTypeRepository
                            );
                        } catch (RepositoryException ex) {
                            
                            
                            logger.warn(() -> "failed to change repository [" + repositoryMetadata.name() + "]", ex);
                            repository = new InvalidRepository(repositoryMetadata, ex);
                        }
                    }
                } else {
                    try {
                        repository = createRepository(repositoryMetadata, typesRegistry, RepositoriesService::createUnknownTypeRepository);