Not able to view submissions in ODK. It shows "Something went wrong: error code 504"

1. What is the issue? Please be detailed.
User is not able to view submissions in ODK Central and getting error message "Something went wrong: error code 504".
This problem occurs when user try to fetch submissions based on selecting particular submitter from filter. For other users it works fine but for a particular user it gives error.

NGINX Logs

  1. 504 Gateway Timed-out nginx
  2. [error] 13#13: *1293 upstream timed out (110: Connection timed out) while reading response header from upstream

2. What steps can we take to reproduce this issue?
NA

3. What have you tried to fix the issue?
Tried to fix it by increasing time out in odk nginx config files but it did not take any effect. Default timeout is set to 2 minute but after increasing timeout still it is being timed out in 2 minute.

4. Upload any forms or screenshots you can share publicly below.

Is your installation done with all default settings? Or have you done additional configurations?

What's the size, resources, and type of your server?