if I just start a odoo16 server , I can have real-time conversations with other users using the discussion feature in Odoo16 and  every thins is fine.

However, after a while , when I log in again and try to chat with the same user, I don't receive real-time messages. I have to refresh the webpage to see new messages. 

But if I restart Odoo instance, I can immediately receive messages without having to refresh the page. 

Based on my description, does any one know where the problem might be?

thanks for any one who read my problems. thanks you.

P.S. 
1.if i log out and after 2-3 minutes, log in , real-time conversations is normal !

2.if i log out and after 15 minutes and more, log in ,real-time conversations is abnormal , But I still can see  [onOpen] and [onMessage] only once, no matter I type any message , I can not see second [onMessage]  in the console , and If now I stop server , I can see [onClose] 1006  and [onError]  every 7 seconds.

3.if I restart odoo16 server , real-time conversations works again but abnormal after 15-20 mins.

4.restart nginx is not working for this situation.

my nginx config is ref to official guide 
System configuration — Odoo 16.0 documentation

my odoo.conf
addons_path= /mnt/extra-addons
data_dir= /var/lib/odoo
list_db= True
proxy_mode= True
max_cron_threads= 1
workers= 2