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
submitUnbatchedTask("put_repository [" + request.name() + "]", new RegisterRepositoryTask(this, request, acknowledgementStep) {
            @Override
            public void onFailure(Exception e) {
                logger.warn(() -> "failed to create repository [" + request.name() + "]", e);
                publicationStep.onFailure(e);
                super.onFailure(e);
            }
            @Override
            public boolean mustAck(DiscoveryNode discoveryNode) {
                
                return discoveryNode.isMasterNode() || discoveryNode.canContainData();
            }
            @Override
            public void clusterStateProcessed(ClusterState oldState, ClusterState newState) {
                if (changed) {
                    if (found) {
                        logger.info("updated repository [{}]", request.name());
                    } else {
                        logger.info("put repository [{}]", request.name());
                    }
                }
                publicationStep.onResponse(oldState != newState);
            }
        });
    }
    /**
     * Task class that extracts the 'execute' part of the functionality for registering
     * repositories.
     */
    public static class RegisterRepositoryTask extends AckedClusterStateUpdateTask {