Still, a little bit confused about what exactly is happening but even if I would fully understand it, I would sadly still be unable to help you here. The reason is simple. Even though I would love to help you, I can sadly not as my Nginx knowledge is more than limited and the problem you are having seems to be Nginx-setup related.
I can just tell you that for me it also looks correct assuming that the IP is correct and what you posted is only part of your setup. So that you have above you also “server” defined with the ports like in this example:
If all that is the case I am sadly also lost. I would probably check with some Nginx people what they think could be going wrong.