Can't access opds-comics via nginx reverse proxy

Hi.

I have ubooquity under windows 10 in a server with 192.168.1.50 ip address and i could access all the resources including opds-comics and opds-books with the explorer in local network.

The problem is when i try to access from internet via nginx reverse proxy. 

My configuration is:

l

ocation /ubqt {
proxy_pass http://192.168.1.50:2202;
proxy_set_header Host $host;
# Permite acceso a los comics por opds
location /ubqt/opds-comics {
auth_request off;
proxy_pass http://192.168.1.50/ubqt/opds-comics/;
}  

The access to "http:\\<internet ip>:port\ubqt" function perfectly, but not the opds-comics.  I use Koobo app in my android tablet and has the same problem. In my local network, works correctly with "http://192.168.1.50:2202/ubqt/opds-comics/"