we upgraded micronaut version from 4.2.1 to 4.7.6 - our kafka producers are not working since the upgrade in staging environment

[anshuhackathon]

Issue description

we upgraded micronaut version from 4.2.1 to 4.7.6 - our kafka producers are not working since the upgrade in staging environment,
Method to produce event is below -

@KafkaClient(id = "test")
public interface DewOfferLDSOEventProducer extends DewAbstractKafkaProducer<DownstreamDTO> {
  @Topic("${test.topic}")
  @Override
  Mono<Object> send(@KafkaKey String key, DownstreamDTO value, Headers headers);

  @Override
  default String getProducerName() {
    return KafkaProducerConstants.LDSO;
  }
}

Below is the error we are seeing in staging environment, Strangely we are not able to replicate it in local machine.

io.micronaut.aop.internal.intercepted.PublisherInterceptedMethod.lambda$convertPublisherResult$2(PublisherInterceptedMethod.java:118)
2025-06-28T06:39:45.567255027Z 	at java.base/java.util.Optional.orElseThrow(Optional.java:403)
2025-06-28T06:39:45.567257833Z 	at io.micronaut.aop.internal.intercepted.PublisherInterceptedMethod.convertPublisherResult(PublisherInterceptedMethod.java:118)
2025-06-28T06:39:45.567260528Z 	at io.micronaut.aop.internal.intercepted.ReactorInterceptedMethod.convertPublisherResult(ReactorInterceptedMethod.java:47)
2025-06-28T06:39:45.567262962Z 	at io.micronaut.aop.internal.intercepted.PublisherInterceptedMethod.handleException(PublisherInterceptedMethod.java:100)
2025-06-28T06:39:45.567265287Z 	at io.micronaut.configuration.kafka.intercept.KafkaClientIntroductionAdvice.intercept(KafkaClientIntroductionAdvice.java:155)
2025-06-28T06:39:45.567268864Z 	at io.micronaut.aop.chain.MethodInterceptorChain.proceed(MethodInterceptorChain.java:143)
2025-06-28T06:39:45.567271429Z 	at com..dew.outbound.offer.eligibility.ldso.kafka.DewOfferEligibilityEventProducer$Intercepted.send(Unknown Source)
2025-06-28T06:39:45.567273793Z 	at com..dew.outbound.offer.eligibility.ldso.kafka.DewOfferEligibilityEventProducer$Intercepted.send(Unknown Source)
2025-06-28T06:39:45.567276117Z 	at com..dew.core.kafka.listener.DewAbstractKafkaListener.lambda$produceMessage$9(DewAbstractKafkaListener.java:196)
2025-06-28T06:39:45.567278592Z 	at reactor.core.publisher.FluxConcatMapNoPrefetch$FluxConcatMapNoPrefetchSubscriber.o

We need quick help to move past this as it has blocked our prod deployment.

[graemerocher]

most likely you are using micronaut-reactor