What can cause duplicate requests to the nginx server?

Question

Nginx

When analyzing access logs, nginx encountered the following:

185.56.17.4 - - [04/Aug/2016:11:58:06 +0000] "POST /api/persist HTTP/1.1" 200 51 "https://game.clickerwarlords.com/platform/fb/?fb_source=sidebar_bookmark" "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/51.0.2704.103 Safari/537.36"
185.56.17.4 - - [04/Aug/2016:11:58:06 +0000] "POST /api/persist HTTP/1.1" 200 51 "https://game.clickerwarlords.com/platform/fb/?fb_source=sidebar_bookmark" "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/51.0.2704.103 Safari/537.36"
185.56.17.4 - - [04/Aug/2016:11:58:06 +0000] "POST /api/persist HTTP/1.1" 200 51 "https://game.clickerwarlords.com/platform/fb/?fb_source=sidebar_bookmark" "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/51.0.2704.103 Safari/537.36"
185.56.17.4 - - [04/Aug/2016:11:58:07 +0000] "POST /api/persist HTTP/1.1" 200 51 "https://game.clickerwarlords.com/platform/fb/?fb_source=sidebar_bookmark" "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/51.0.2704.103 Safari/537.36"

From the same client, a request to the server sometimes comes several times in a row, and this despite the fact that the client at this address is contacted once after the main content is loaded.
What could be causing this and what are the ways to fix it.

Answer 1

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