Strange behavior of Nginx. Through times gives page from cache. How can I disable caching for this page?

Question

Nginx

Hello. Faced the following problem. Changed the Robots.txt file. After it was poured onto the server, a problem was discovered that neither Yandex nor Google see the changes. Although I, when entering the page, I see them. After I noticed that with frequent page updates, the old version of the file is periodically issued, then the new one. Caches deleted everything according to this instruction
find /var/cache/nginx/proxy/ -type f -delete:.
Did not help. added to location

proxy_pass_request_body off;
proxy_pass_request_headers off;
proxy_redirect off;

Did not help. I read that you need to add "proxy_no_cache" or "proxy_cache_bypass". But I can't figure out how to set these commands to a specific page.

Answer 1

It looks more like you have several backends and the file has not been updated on one of them.
Where does proxy_pass lead to?