Hi there. Getting error 502 while trying open template style from backend:

2019/06/17 15:58:14 [error] 684#684: *44 upstream sent too big header while reading response header from upstream, client: 10.0.0.7, server: t4framework.loc, request: "GET /administrator/index.php?option=com_templates&view=style&layout=edit&id=$
2019/06/17 16:02:32 [error] 684#684: *67 FastCGI sent in stderr: "PHP message: PHP Warning:  file_get_contents(): SSL operation failed with code 1. OpenSSL Error messages:
error:1416F086:SSL routines:tls_process_server_certificate:certificate verify failed in /home/eugene/att/www/plugins/system/t4/admin/field/googlefonts.php on line 155
PHP message: PHP Warning:  file_get_contents(): Failed to enable crypto in /home/eugene/att/www/plugins/system/t4/admin/field/googlefonts.php on line 155
PHP message: PHP Warning:  file_get_contents(https://t4framework.loc/plugins/system/t4/admin/assets/js/basefonts.json): failed to open stream: operation failed in /home/eugene/att/www/plugins/system/t4/admin/field/googlefonts.php on line 155
PHP message: PHP Warning:  file_get_contents(): SSL operation failed with code 1. OpenSSL Error messages:
error:1416F086:SSL routines:tls_process_server_certificate:certificate verify failed in /home/eugene/att/www/plugins/system/t4/admin/field/googlefonts.php on line 65
PHP message: PHP Warning:  file_get_contents(): Failed to enable crypto in /home/eugene/att/www/plugins/system/t4/admin/field/googlefonts.php on line 65
PHP message: PHP Warning:  file_get_contents(https://t4framework.loc/plugins/system/t4/admin/assets/js/fonts.json): failed to open stream: operation failed in /home/eugene/att/www/plugins/system/t4/admin/field/googlefonts.php on line 65
PHP message: PHP Warning:  file_get_contents(): SSL operation failed with code 1. OpenSSL Error messages:
error:1416F086:SSL routines:tls_process_server_certificate:certificate verify failed in /home/eugene/att/www/plugins/system/t4/admin/field/googlefonts.php on line 68
PHP message: PHP Warning:  file_get_contents(): Failed to enable crypto in /home/eugene/att/www/plugins/system/t4/admin/field/googlefonts.php on line 68
PHP message: PHP Warning:  file_get_contents(https://t4framework.loc/plugins/system/t4/admin/assets/js/basefonts.json): failed to open stream: operation failed in /home/eugene/att/www/plugins/system/t4/admin/field/googlefonts.php on line 68

System Information

PHP Built On	Linux debian 4.9.0-8-amd64 #1 SMP Debian 4.9.144-3.1 (2019-02-19) x86_64
Database Type	mysql
Database Version	5.5.5-10.1.26-MariaDB
Database Collation	utf8_general_ci
Database Connection Collation	utf8mb4_general_ci
PHP Version	7.2.13-1
Web Server	nginx/1.10.3
WebServer to PHP Interface	fpm-fcgi
Joomla! Version	Joomla! 3.9.8 Stable [ Amani ] 11-June-2019 20:00 GMT
Joomla! Platform Version	Joomla Platform 13.1.0 Stable [ Curiosity ] 24-Apr-2013 00:00 GMT
User Agent	Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/74.0.3729.169 Safari/537.36

This local server. Same config online working fine. Thing is I want to test everything on local server, so maybe you can reproduce this error and check what is going on. Certificate is free Let's Encrypt.

Thank you for your help!