Приложение Nginx + Docker + DotNet на тайм-ауте запроса Ubuntu 16.04

У меня есть среда Ubuntu 16.04 с Docker в Digital Ocean, и я загружаю службу с помощью docker-compose:

version: '2'
services:
  cis-api:
    image: docker.myserver.com/cis-api:latest
    ports:
      - 8080:5000
    environment:
      DB_CONN_STRING: 'Server=tcp:...;Initial Catalog=cis-stage;Persist Security Info=False;User ID=...;Password=...;MultipleActiveResultSets=False;Encrypt=True;TrustServerCertificate=False;Connection Timeout=30;'

Затем у меня установлен ванильный Nginx с одной конфигурацией внутри /etc/nginx/conf.d:

upstream cis-api {
  server 0.0.0.0:8080;
}

server {
  listen 80;
  server_name cis-api.myserver.com;

  location / {
    proxy_pass                          http://cis-api;
    proxy_set_header  Host              $http_host;   # required for docker client's sake
    proxy_set_header  X-Real-IP         $remote_addr; # pass on real client's IP
    proxy_set_header  X-Forwarded-For   $proxy_add_x_forwarded_for;
    proxy_set_header  X-Forwarded-Proto $scheme;
    proxy_read_timeout                  900;
  }
}

Когда я пытаюсь запросить URL в обход nginx, все работает:

root@cis-stage:/etc/nginx# curl localhost:8080/businesses -H 'Authorization: Bearer ...'
[{"id":1,...,"email":null}]

Однако, если я попытаюсь выполнить тот же запрос, проходящий через nginx, соединение зависнет, или если я установлю тайм-аут 30 секунд, он истечет:

root@cis-stage:/etc/nginx# curl --max-time 30 --connect-timeout 30 http://cis-api.mysever.com/businesses -H 'Authorization: Bearer ....'

curl: (28) Operation timed out after 30000 milliseconds with 0 bytes received

Приложение написано на ASP.Net Core 1.1, и вот разница в результатах, когда я запускаю его в обход nginx:

cis-api_1  | dbug: Microsoft.AspNetCore.Server.Kestrel[1]
cis-api_1  |       Connection id "0HL3OL7D1CF19" started.
cis-api_1  | info: Microsoft.AspNetCore.Hosting.Internal.WebHost[1]
cis-api_1  |       Request starting HTTP/1.1 GET http://localhost:8080/businesses
cis-api_1  | info: Microsoft.AspNetCore.Authentication.JwtBearer.JwtBearerMiddleware[2]
cis-api_1  |       Successfully validated the token.
cis-api_1  | info: Microsoft.AspNetCore.Authentication.JwtBearer.JwtBearerMiddleware[3]
cis-api_1  |       HttpContext.User merged via AutomaticAuthentication from authenticationScheme: Bearer.
cis-api_1  | info: Microsoft.AspNetCore.Hosting.Internal.WebHost[2]
cis-api_1  |       Request finished in 414.6261ms 200 application/json; charset=utf-8
cis-api_1  | dbug: Microsoft.AspNetCore.Server.Kestrel[6]
cis-api_1  |       Connection id "0HL3OL7D1CF19" received FIN.
cis-api_1  | dbug: Microsoft.AspNetCore.Server.Kestrel[9]
cis-api_1  |       Connection id "0HL3OL7D1CF19" completed keep alive response.
cis-api_1  | dbug: Microsoft.AspNetCore.Server.Kestrel[10]
cis-api_1  |       Connection id "0HL3OL7D1CF19" disconnecting.
cis-api_1  | dbug: Microsoft.AspNetCore.Server.Kestrel[7]
cis-api_1  |       Connection id "0HL3OL7D1CF19" sending FIN.
cis-api_1  | dbug: Microsoft.AspNetCore.Server.Kestrel[8]
cis-api_1  |       Connection id "0HL3OL7D1CF19" sent FIN with status "0".
cis-api_1  | dbug: Microsoft.AspNetCore.Server.Kestrel[2]
cis-api_1  |       Connection id "0HL3OL7D1CF19" stopped.

Против, когда я использую nginx в качестве прокси:

cis-api_1  | dbug: Microsoft.AspNetCore.Server.Kestrel[1]
cis-api_1  |       Connection id "0HL3OL7D1CF1B" started.
cis-api_1  | info: Microsoft.AspNetCore.Hosting.Internal.WebHost[1]
cis-api_1  |       Request starting HTTP/1.0 GET http://cis-api.myserver.com/businesses
cis-api_1  | info: Microsoft.AspNetCore.Authentication.JwtBearer.JwtBearerMiddleware[2]
cis-api_1  |       Successfully validated the token.
cis-api_1  | info: Microsoft.AspNetCore.Authentication.JwtBearer.JwtBearerMiddleware[3]
cis-api_1  |       HttpContext.User merged via AutomaticAuthentication from authenticationScheme: Bearer.

Здесь он висит до истечения времени ожидания запроса, а затем:

cis-api_1  | dbug: Microsoft.AspNetCore.Server.Kestrel[6]
cis-api_1  |       Connection id "0HL3OLAD6F4QN" received FIN.
cis-api_1  | info: Microsoft.AspNetCore.Hosting.Internal.WebHost[2]
cis-api_1  |       Request finished in 4615.4522ms 200 application/json; charset=utf-8
cis-api_1  | dbug: Microsoft.AspNetCore.Server.Kestrel[10]
cis-api_1  |       Connection id "0HL3OLAD6F4QN" disconnecting.
cis-api_1  | dbug: Microsoft.AspNetCore.Server.Kestrel[7]
cis-api_1  |       Connection id "0HL3OLAD6F4QN" sending FIN.
cis-api_1  | dbug: Microsoft.AspNetCore.Server.Kestrel[8]
cis-api_1  |       Connection id "0HL3OLAD6F4QN" sent FIN with status "-107".
cis-api_1  | dbug: Microsoft.AspNetCore.Server.Kestrel[2]
cis-api_1  |       Connection id "0HL3OLAD6F4QN" stopped.

Любые идеи?