@rshabalin, это access.log — если перевести, то это просто логи доступа. И судя по ним, ошибка 500 у вас что-то слишком часто, и на страницах, которых нет в теме...
В access.log текст ошибки не попадает. Нужен error.log
2021/02/03 13:54:07 [error] 7226#7226: *899 "/var/www/rshabalin/data/www/rybalka-kirov.ru/index.php" is forbidden (13: Permission denied), client: 178.141.233.202, server: rybalka-kirov.ru, request: "GET / HTTP/1.1", host: "rybalka-kirov.ru"
2021/02/03 13:54:07 [crit] 7226#7226: *899 openat() "/var/www/rshabalin/data/www/rybalka-kirov.ru/favicon.ico" failed (13: Permission denied), client: 178.141.233.202, server: rybalka-kirov.ru, request: "GET /favicon.ico HTTP/1.1", host: "rybalka-kirov.ru", referrer: "rybalka-kirov.ru/"
2021/02/03 13:54:07 [crit] 7226#7226: *899 openat() "/var/www/rshabalin/data/www/rybalka-kirov.ru/favicon.ico" failed (13: Permission denied), client: 178.141.233.202, server: rybalka-kirov.ru, request: "GET /favicon.ico HTTP/1.1", host: "rybalka-kirov.ru", referrer: "rybalka-kirov.ru/"
2021/02/03 13:54:07 [error] 7226#7226: *899 FastCGI sent in stderr: "Access to the script '/var/www/rshabalin/data/www/rybalka-kirov.ru/favicon.ico' has been denied (see security.limit_extensions)" while reading response header from upstream, client: 178.141.233.202, server: rybalka-kirov.ru, request: "GET /favicon.ico HTTP/1.1", upstream: "fastcgi://unix:/var/run/rybalka-kirov.ru.sock:", host: "rybalka-kirov.ru", referrer: "rybalka-kirov.ru/"
2021/02/03 13:54:19 [error] 7226#7226: *899 "/var/www/rshabalin/data/www/rybalka-kirov.ru/index.php" is forbidden (13: Permission denied), client: 178.141.233.202, server: rybalka-kirov.ru, request: "GET / HTTP/1.1", host: "rybalka-kirov.ru"
2021/02/03 13:54:20 [error] 7226#7226: *901 "/var/www/rshabalin/data/www/rybalka-kirov.ru/index.php" is forbidden (13: Permission denied), client: 178.141.233.202, server: rybalka-kirov.ru, request: "GET / HTTP/1.1", host: "rybalka-kirov.ru"
2021/02/03 13:54:21 [crit] 7226#7226: *901 openat() "/var/www/rshabalin/data/www/rybalka-kirov.ru/favicon.ico" failed (13: Permission denied), client: 178.141.233.202, server: rybalka-kirov.ru, request: "GET /favicon.ico HTTP/1.1", host: "rybalka-kirov.ru", referrer: "rybalka-kirov.ru/"
2021/02/03 13:54:21 [crit] 7226#7226: *901 openat() "/var/www/rshabalin/data/www/rybalka-kirov.ru/favicon.ico" failed (13: Permission denied), client: 178.141.233.202, server: rybalka-kirov.ru, request: "GET /favicon.ico HTTP/1.1", host: "rybalka-kirov.ru", referrer: "rybalka-kirov.ru/"
2021/02/03 13:54:21 [error] 7226#7226: *901 FastCGI sent in stderr: "Access to the script '/var/www/rshabalin/data/www/rybalka-kirov.ru/favicon.ico' has been denied (see security.limit_extensions)" while reading response header from upstream, client: 178.141.233.202, server: rybalka-kirov.ru, request: "GET /favicon.ico HTTP/1.1", upstream: "fastcgi://unix:/var/run/rybalka-kirov.ru.sock:", host: "rybalka-kirov.ru", referrer: "rybalka-kirov.ru/"
2021/02/03 13:54:21 [error] 7226#7226: *903 "/var/www/rshabalin/data/www/rybalka-kirov.ru/index.php" is forbidden (13: Permission denied), client: 178.141.233.202, server: rybalka-kirov.ru, request: "GET / HTTP/1.1", host: "rybalka-kirov.ru"
2021/02/03 13:54:21 [crit] 7226#7226: *903 openat() "/var/www/rshabalin/data/www/rybalka-kirov.ru/favicon.ico" failed (13: Permission denied), client: 178.141.233.202, server: rybalka-kirov.ru, request: "GET /favicon.ico HTTP/1.1", host: "rybalka-kirov.ru", referrer: "rybalka-kirov.ru/"
2021/02/03 13:54:21 [crit] 7226#7226: *903 openat() "/var/www/rshabalin/data/www/rybalka-kirov.ru/favicon.ico" failed (13: Permission denied), client: 178.141.233.202, server: rybalka-kirov.ru, request: "GET /favicon.ico HTTP/1.1", host: "rybalka-kirov.ru", referrer: "rybalka-kirov.ru/"
2021/02/03 13:54:21 [error] 7226#7226: *903 FastCGI sent in stderr: "Access to the script '/var/www/rshabalin/data/www/rybalka-kirov.ru/favicon.ico' has been denied (see security.limit_extensions)" while reading response header from upstream, client: 178.141.233.202, server: rybalka-kirov.ru, request: "GET /favicon.ico HTTP/1.1", upstream: "fastcgi://unix:/var/run/rybalka-kirov.ru.sock:", host: "rybalka-kirov.ru", referrer: "rybalka-kirov.ru/"
2021/02/03 13:54:23 [error] 7226#7226: *905 "/var/www/rshabalin/data/www/rybalka-kirov.ru/index.php" is forbidden (13: Permission denied), client: 178.141.233.202, server: rybalka-kirov.ru, request: "GET / HTTP/1.1", host: "rybalka-kirov.ru"
2021/02/03 13:54:23 [crit] 7226#7226: *905 openat() "/var/www/rshabalin/data/www/rybalka-kirov.ru/favicon.ico" failed (13: Permission denied), client: 178.141.233.202, server: rybalka-kirov.ru, request: "GET /favicon.ico HTTP/1.1", host: "rybalka-kirov.ru", referrer: "rybalka-kirov.ru/"
2021/02/03 13:54:23 [crit] 7226#7226: *905 openat() "/var/www/rshabalin/data/www/rybalka-kirov.ru/favicon.ico" failed (13: Permission denied), client: 178.141.233.202, server: rybalka-kirov.ru, request: "GET /favicon.ico HTTP/1.1", host: "rybalka-kirov.ru", referrer: "rybalka-kirov.ru/"
2021/02/03 13:54:23 [error] 7226#7226: *905 FastCGI sent in stderr: "Access to the script '/var/www/rshabalin/data/www/rybalka-kirov.ru/favicon.ico' has been denied (see security.limit_extensions)" while reading response header from upstream, client: 178.141.233.202, server: rybalka-kirov.ru, request: "GET /favicon.ico HTTP/1.1", upstream: "fastcgi://unix:/var/run/rybalka-kirov.ru.sock:", host: "rybalka-kirov.ru", referrer: "rybalka-kirov.ru/"
2021/02/03 13:54:58 [error] 7226#7226: *907 "/var/www/rshabalin/data/www/rybalka-kirov.ru/index.php" is forbidden (13: Permission denied), client: 88.214.230.106, server: rybalka-kirov.ru, request: "GET / HTTP/1.1", host: "rybalka-kirov.ru"
2021/02/03 13:55:01 [error] 7226#7226: *908 "/var/www/rshabalin/data/www/rybalka-kirov.ru/index.php" is forbidden (13: Permission denied), client: 109.95.209.21, server: rybalka-kirov.ru, request: "GET / HTTP/1.1", host: "rybalka-kirov.ru"
2021/02/03 13:55:04 [error] 7226#7226: *909 "/var/www/rshabalin/data/www/rybalka-kirov.ru/index.php" is forbidden (13: Permission denied), client: 195.42.181.27, server: rybalka-kirov.ru, request: "GET / HTTP/1.1", host: "rybalka-kirov.ru"
2021/02/03 13:56:02 [error] 7226#7226: *917 "/var/www/rshabalin/data/www/rybalka-kirov.ru/index.php" is forbidden (13: Permission denied), client: 45.144.3.180, server: rybalka-kirov.ru, request: "GET / HTTP/1.1", host: "rybalka-kirov.ru"
2021/02/03 13:58:14 [crit] 7226#7226: *920 openat() "/var/www/rshabalin/data/www/rybalka-kirov.ru/favicon.ico" failed (13: Permission denied), client: 178.141.233.202, server: rybalka-kirov.ru, request: "GET /favicon.ico?1612349895309 HTTP/1.1", host: "rybalka-kirov.ru"
2021/02/03 13:58:14 [crit] 7226#7226: *920 openat() "/var/www/rshabalin/data/www/rybalka-kirov.ru/favicon.ico" failed (13: Permission denied), client: 178.141.233.202, server: rybalka-kirov.ru, request: "GET /favicon.ico?1612349895309 HTTP/1.1", host: "rybalka-kirov.ru"
2021/02/03 13:58:14 [error] 7226#7226: *920 FastCGI sent in stderr: "Access to the script '/var/www/rshabalin/data/www/rybalka-kirov.ru/favicon.ico' has been denied (see security.limit_extensions)" while reading response header from upstream, client: 178.141.233.202, server: rybalka-kirov.ru, request: "GET /favicon.ico?1612349895309 HTTP/1.1", upstream: "fastcgi://unix:/var/run/rybalka-kirov.ru.sock:", host: "rybalka-kirov.ru"
но мало-ли. А папки отключить, у вас вообще пропадут они при добавление. Версия какая InstantCMS, последняя? Если нет, обновить.