Unknown reason triggers .doOnCancel(() -> cleanup(exchange)) in NettyWriteResponseFilter occasionally

Describe the bug
Spring Cloud Gateway version:2.2.5
reactor-netty version :0.9.15

• Use method ServerHttpResponse.writeWith(Mono<DataBuffer> instead of ServerHttpResponse.writeWith(Flux<DataBuffer>) in NettyWriteResponseFilter.java in high-concurrency scenarios triggers doOnCancel(() -> cleanup(connection)) occasionally
• Method doOnCancel(() -> cleanup(connection)) will close the long connection between the gateway and downstream services, and this closure will not be monitored by the connection pool status, resulting in subsequent requests generating exception reactor.netty.channel.AbortedException: Connection has been closed BEFORE response while sending request body

Describe the solution you'd like

• Understanding the root cause of mono triggering doOnCancel
• Connection pool can monitor connection status when the connection is closed

Sample

public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
    return chain.filter(exchange)
        
        .doOnError(throwable -> cleanup(exchange))
        .then(Mono.defer(() -> {
            
            Connection connection = exchange.getAttribute(CLIENT_RESPONSE_CONN_ATTR);
            if (connection == null) {
                return Mono.empty();
            }
            ServerHttpResponse response = exchange.getResponse();
            
            final Flux<DataBuffer> body = connection
                .inbound()
                .receive()
                .retain()
                .map(byteBuf -> wrap(byteBuf, response));

            // My changes are here
            Mono<DataBuffer> newBody = body.single();
            MediaType contentType = null;
            try {
                contentType = response.getHeaders().getContentType();
            }
            catch (Exception e) {}
           
            return (isStreamingMediaType(contentType)
                ? response.writeAndFlushWith(body.map(Flux::just))
                : response.writeWith(newBody));
        })).doOnCancel(() -> cleanup(exchange));
}

Start in NettyWriteResponseFilter.java and compare the reported writeWith(Mono) path with the Flux path. Reproduce the high-concurrency scenario and trace when doOnCancel(() -> cleanup(exchange)) runs. Done means the cancellation cause is understood and connection closure is correctly reflected in connection-pool status.