IncrementRequest TIMEOUT

Java SDK
1

I use Community Edition 6.0.0 cluster with two cocuhbase server and Java SDK ver 3.4.0 and Spring Webflux.
I call saveSomeObject function at Service layer

public Mono<SomeObject> saveSomeObject(SomeObject campaign){
      return basicFactorsBucket.reactive()
                .viewQuery(CouchbaseDesign.ZONE, CouchbaseView.BY_COUNTRY_CODE, viewOptions)
                .flatMapMany(ReactiveViewResult::rows)
                .filter(viewRow -> viewRow.id().isPresent())
                .flatMap(viewRow -> basicFactorsBucket.reactive().defaultCollection()
                    .get(viewRow.id().get()))
                .map(GetResult::contentAsObject)
                .map(json -> {
                    //.. make some Object
                    SomeObject obj = ...;
                    
                    return obj;
                })
                .collect(ConcurrentHashMap<String, SomeObject>::new, (map, task) -> {
                    String key = task.time();

                    if (map.containsKey(key)) {
                        map.get(key).zones().add(task.zones().getFirst());
                    } else {
                        map.put(key, task);
                    }
                })
                .map(tasks -> {
                    // DO some process...
                    
                    Long counter = campaignBucket.defaultCollection().binary()
                            .increment("campaignCounter",
                                IncrementOptions.incrementOptions().delta(1).initial(1).timeout(
                                    Duration.ofMillis(2000))).content();
                                    
                    campaignId = counter;
                    campaignBucket.defaultCollection()
                        .upsert(String.format("campaign::%d", campaignId), jsonObject);

                    return campaign;
                })
                .doOnError(error -> log.error(error.getMessage()))
                .onErrorResume(error -> {
                    log.error(error.getMessage());
                    return Mono.error(new InternalServerErrorException(error.getMessage()));
                });
}

Then some times occure under error log.
It doesn’t happen every time.

 IncrementRequest, Reason: TIMEOUT {"cancelled":true,"completed":true,"coreId":"0x56a0a28600000001","idempotent":false,"lastChannelId":"56A0A28600000001/00000000FE2E258E","lastDispatchedFrom":"SERVER IP:27434","lastDispatchedTo":"SERVER IP:11210","reason":"TIMEOUT","requestId":59414,"requestType":"IncrementRequest","retried":0,"service":{"bucket":"Campaigns","collection":"_default","documentId":"campaignCounter","opaque":"0xe7e4","scope":"_default","type":"kv","vbucket":751},"timeoutMs":2000,"timings":{"totalMicros":2010700}}

and Really sometimes the below error also occurs. But there is no problem.

2023:03:30 10:01:02.856 ERROR 2515106 --- [reactor-http-server-epoll-5] reactor.core.publisher.Operators[error:324] : Operator called default onErrorDropped
io.netty.channel.unix.Errors$NativeIoException: syscall:read(..) failed: Connection reset by peer
        at io.netty.channel.unix.FileDescriptor.readAddress(..)(Unknown Source)

When calling Increment on the third map, it is suspected that the above phenomenon occurs because it does not bucket reactive().
plz help me why some times occure Increment TIMEOUT Error and Operator called default onErrorDropped.