Errors in nginx and apache logs

[presta_newbie]

Hi there.
I faced with amount of errors in nginx and apache logs.
Here is my installation:

• Hestia control panel 1.6.14
• Ubuntu 20
• Apache/2.4.54
• nginx/1.23.2
• php-fpm 7
• PrestaShop 1.6.1.24

Nginx errors look like that

2023/03/02 07:51:02 [error] 2921755#2921755: *1905725 recv() failed (104: Connection reset by peer) while reading response header from upstream, client: 66.249.70.175, server: my_DNS_name, request: "GET /29804-zoom_image/rca-razyom-wbt-0152-ag.webp HTTP/1.1", upstream: "http://185.121.165.57:8080/29804-zoom_image/rca-razyom-wbt-0152-ag.webp", host: "my_DNS_name"

From what I found in Internet it mean that apache returned abnormal response to nginx (which act as a proxy)

And Apache errors look like that

[Fri Mar 03 14:08:44.732572 2023] [proxy_fcgi:error] [pid 3415876:tid 139688752957184] [client 185.191.171.2:0] AH01071: Got error 'PHP message: PHP Notice:  Trying to get property of non-object in /home/user/web/my_DNS_name/public_html/cache/smarty/compile/0c/e8/a6/0ce8a6f6e847ca40c453831a25a53e2300eaf98d.file.productcomments.tpl.php on line 58\nPHP message: PHP Notice:  Trying to get property of non-object in /home/user/web/my_DNS_name/public_html/cache/smarty/compile/0c/e8/a6/0ce8a6f6e847ca40c453831a25a53e2300eaf98d.file.productcomments.tpl.php on line 60\nPHP message: PHP Notice:  Trying to get property of non-object in /home/user/web/my_DNS_name/public_html/cache/smarty/compile/0c/e8/a6/0ce8a6f6e847ca40c453831a25a53e2300eaf98d.file.productcomments.tpl.php on line 63\n'


[Fri Mar 03 12:14:08.307933 2023] [authz_core:error] [pid 3415876:tid 139689549870848] [client 66.249.79.91:0] AH01630: client denied by server configuration: /home/user/web/my_DNS_name/public_html/img/p/1/5/1/0/0

These errors mean that there is no object or no access to it. I checked "/home/user/web/my_DNS_name/public_html/cache/smarty/compile/" folder and "/home/user/web/my_DNS_name/public_html/img/p/" folder and there are a lot of files created during last 24 hours. So I can assume, that there is a write permission for these folders.

Sometimes my site is unreachable, but I don't know where to dig further. Any ideas how to investigate that issue?