Zuul Response filter getting blocked for sometime intermittently

Question

We are using zuul 2.1.6 without eureka and we got the response back form down stream API but it's getting blocked for some reason in the response/outbound filter sometimes (not all the time). It's happening intermittently and the CPU also not used much during these times. What could be the root cause? Anyone faced a scenario like this? Thank in advance for any suggestions..

Below is how the response filter looks like

@OverRide
HttpResponseMessage apply(HttpResponseMessage response) {
SessionContext context = response.getContext()
if (SEND_RESPONSE_HEADERS.get()) {
    Headers headers = response.getHeaders()

    StatusCategory statusCategory = StatusCategoryUtils.getStatusCategory(response)
    if (statusCategory != null) {
        headers.set(X_ZUUL_STATUS, statusCategory.name())
    }

    RequestAttempts attempts = RequestAttempts.getFromSessionContext(response.getContext())
    String headerStr = ""
    if (attempts != null) {
        headerStr = attempts.toString()
    }
    headers.set(X_ZUUL_PROXY_ATTEMPTS, headerStr)

    headers.set(X_ZUUL, "zuul")
    headers.set(X_ZUUL_INSTANCE, System.getenv("EC2_INSTANCE_ID") ?: "unknown")
    headers.set(CONNECTION, KEEP_ALIVE)
    headers.set(X_ZUUL_FILTER_EXECUTION_STATUS, context.getFilterExecutionSummary().toString())
    headers.set(X_ORIGINATING_URL, response.getInboundRequest().reconstructURI())

    log.info("status:"+ attempts.get(0).getStatus()+" duration:"+ attempts.get(0).getDuration())

    if (response.getStatus() >= 400 && context.getError() != null) {
        Throwable error = context.getError()
        headers.set(X_ZUUL_ERROR_CAUSE,
                error instanceof ZuulException ? ((ZuulException) error).getErrorCause() :     "UNKNOWN_CAUSE")
    }

    if (response.getStatus() >= 400) {
        log.info("Passport: {}", CurrentPassport.fromSessionContext(context))
    }
}

if (context.debugRequest()) {
    Debug.getRequestDebug(context).forEach({ s -> log.info("REQ_DEBUG: " + s) })
    Debug.getRoutingDebug(context).forEach({ s -> log.info("ZUUL_DEBUG: " + s) })
}

return response

}

}

Let's say The status log which is after the headers.set got logged at 28-11-23 19:30:10 and the passport log, which is after few lines getting logged at 28-11-23 19:30:20. it is taking/blocked for 10 secs there.

Tried increasing the ribbon read timeout and netty thread counts, still seeing the issue.