nginx report connect failed 10060 after running for a period of time - nginx

Question

I deployed a nginx service on windows server to proxy http requests,here is my nginx config:
worker_processes 1;
#error_log logs/error.log;
#error_log logs/error.log notice;
#error_log logs/error.log info;
#pid logs/nginx.pid;
events {
worker_connections 1024;
}
http {
include mime.types;
default_type application/octet-stream;
#log_format main '$remote_addr - $remote_user [$time_local] "$request" '
# '$status $body_bytes_sent "$http_referer" '
# '"$http_user_agent" "$http_x_forwarded_for"';
#access_log logs/access.log main;
sendfile on;
#tcp_nopush on;
#keepalive_timeout 0;
keepalive_timeout 60000;
gzip on;
gzip_min_length 10k;
gzip_buffers 4 16k;
gzip_http_version 1.1;
gzip_comp_level 5;
gzip_types text/plain application/x-javascript text/css application/xml text/javascript application/x-httpd-php application/javascript application/json;
gzip_disable "MSIE [1-6]\.";
gzip_vary on;
location /api/{
proxy_pass http://www.******.com/;
proxy_read_timeout 3600s;
proxy_send_timeout 3600s;
}
}
But every time after running for a few days, the following error message will appear:
8480#12136: *32175 connect() failed (10060: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond) while connecting to upstream, client: 172.10.2.100, server: , request: "POST /api/address/someapi HTTP/1.1", upstream: "http://222.218.***.**:80/address/xxxxxx", host: "341o932a61.xxx.vip"
When I restart nginx, everything goes back to normal.
What is the reason for this?
Environment:
System: Windows Server 2019 Standard 1809
Nginx: 1.20.1