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/cluster/metadata/RepositoryMetadata.java
private final String name;
    private final String uuid;
    private final String type;
    private final Settings settings;
    /**
     * Safe repository generation.
     */
    private final long generation;
    /**
     * Pending repository generation.
     */
    private final long pendingGeneration;
    /**
     * Constructs new repository metadata
     *
     * @param name     repository name
     * @param type     repository type
     * @param settings repository settings
     */
    public RepositoryMetadata(String name, String type, Settings settings) {