Getting Error 502 - Bad Gateway on one route


I am getting Error 502 - Bad Gateway one route, and other routes are working fine. I checked my code and I did not found anything wrong. Furthermore, route was working fine when I created, and then suddenly it started throwing this error. Here are picture of error and code:
There is only one error in chrome developer console : Failed to load resource: the server responded with a status of 502 (Bad Gateway) and then patth.
error picture:

code picutre: I was not allow to post more than one picture in one post because I am new here/