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
name,
                    repository.getMetadata().type(),
                    name,
                    type
                )
            );
        } else if (repositories.containsKey(name)) {
            logger.warn(
                () -> format(
                    "non-internal repository [%s] already registered. this repository will block the "
                        + "usage of internal repository [%s][%s].",
                    name,
                    metadata.type(),
                    name
                )
            );
        }
    }
    public void unregisterInternalRepository(String name) {
        Repository repository = internalRepositories.remove(name);
        if (repository != null) {
            RepositoryMetadata metadata = repository.getMetadata();
            logger.debug(() -> format("delete internal repository [%s][%s].", metadata.type(), name));
            closeRepository(repository);
        }
    }
    /**
     * Closes the given repository.
     */
    private static void closeRepository(Repository repository) {