More info on StackOverflow: https://stackoverflow.com/questions/78989281/spring-integration-webflux-fails-for-every-other-calls. Fix the `AbstractHttpRequestExecutingMessageHandler` to remove a `Content-Length` when: ``` if (!shouldIncludeRequestBody(httpMethod)) { return new HttpEntity<>(httpHeaders); } ``` The workaround is to remove this header before calling WebFlux outbound channel adapter: ``` .headerFilter("Content-Length") ```