Unexpected error 502 Bad Gateway, how to solve?

Question

MODX

Hello.
Error 502 began to appear only on one page with its template, only after clearing the cache, if you go to another page and return, then the error teaches. Loaded a page with blank templates the same thing.
Errors are not displayed in the engine and hosting, also included pdotools_fenom_save_on_errors, empty everywhere.
People.
How can I catch this problem?

Answer 1

And if you hang this template on another resource, the error is the same?