Why is nginx giving 410 error?

Question

Nginx

We have an application on laravel. We are
trying to integrate with Tinkoff Payment, in which payment notifications come to our URL (in the form of json), and we must respond with a 200 code and the text OK (as, in fact, in other payment systems)
The problem is that Tinkoff sends requests to us and receives a 410 error in response (judging by the access logs).
In the application, we add dumps of such requests to the log. But for some reason the log is empty. Apparently the request falls off with code 410 even before it reaches the application, at the apache / nginx level.
I try to send requests through postman - 200OK, I try stupidly through the browser - 200OK.
91.194.XXX.XXX - - [26/Apr/2019:11:48:55 +0300] "POST /payment/tinkoff/process HTTP/1.1" 410 170 "-" "Apache-HttpClient/4.5.5 (Java/ 1.8.0_73)"
91.194.XXX.XXX - - [26/Apr/2019:11:48:55 +0300] "POST /payment/tinkoff/process HTTP/1.1" 410 170 "-" "Apache-HttpClient/4.5.5 (Java/ 1.8.0_73)"
81.28.ХХХ.ХХХ - - [26/Apr/2019:09:26:52 +0300] "POST /payment/tinkoff/process HTTP/1.0" 200 927 "-" "PostmanRuntime/7.6.1 "
Where to dig?

Answer 1

We turned to the hoster, it turned out that on our side there was some kind of anti-bot filter that drops everyone whose user-agent contains "Java".
So it goes