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/internalClusterTest/java/org/elasticsearch/snapshots/ConcurrentSnapshotsIT.java
createFullSnapshot(repoName, "empty-snapshot");
        
        
        createIndexWithContent("index-test", indexSettingsNoReplicas(randomIntBetween(6, 10)).build());
        final NetworkDisruption networkDisruption = isolateMasterDisruption(NetworkDisruption.DISCONNECT);
        internalCluster().setDisruptionScheme(networkDisruption);
        final List<String> fullSnapshotsToDelete = createNSnapshots(repoName, randomIntBetween(1, 5));
        final String masterName = internalCluster().getMasterName();
        blockMasterFromDeletingIndexNFile(repoName);
        final ActionFuture<AcknowledgedResponse> deleteAllSnapshotsWithIndex = startDeleteSnapshots(
            repoName,
            fullSnapshotsToDelete,
            masterName
        );
        
        awaitNDeletionsInProgress(1);
        final ActionFuture<CreateSnapshotResponse> snapshotFuture = startFullSnapshotFromDataNode(repoName, "new-full-snapshot");
        waitForBlock(masterName, repoName);
        awaitNumberOfSnapshotsInProgress(1);
        networkDisruption.startDisrupting();
        ensureStableCluster(3, dataNode);
        
        try {
            snapshotFuture.get();
        } catch (Exception e) {
            
            
            
        }
        awaitNoMoreRunningOperations(dataNode);