More Detailed Error logging on Failure to use PHP GD Library Function

Been posting about it here https://github.com/Intervention/image/issues/926 . I am using Laradock with PHP-FPM and Nginx. Each time I use the GD library to manipulate images with Laravel and Image Intervention I get an error 500 before or on start of using a resize method.

I get no other useful errors at all besides that error 500. According to php info and some other checks the GD Library is up and running. And there do not seem to be permission issues as I can manipulate images with Imagemagick and as the first step (storing original and basic thumbnail) do work.

Here is my currently using default.conf

server {

listen 80 default_server;
listen [::]:80 default_server ipv6only=on;

# For https
listen 443 ssl default_server;
listen [::]:443 ssl default_server ipv6only=on;
ssl_certificate /etc/nginx/ssl/default.crt;
ssl_certificate_key /etc/nginx/ssl/default.key;

server_name localhost;
root /var/www/public;
index index.php index.html index.htm;

location / {
try_files $uri $uri/ /index.php$is_args$args;
}

location ~ \.php$ {
try_files $uri /index.php =404;
fastcgi_pass php-upstream;
fastcgi_index index.php;
fastcgi_buffers 16 16k;
fastcgi_buffer_size 32k;
fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
#fixes timeouts
fastcgi_read_timeout 600;
include fastcgi_params;
}

location ~ /\.ht {
deny all;
}

location /.well-known/acme-challenge/ {
root /var/www/letsencrypt/;
log_not_found off;
}
}

It the one included by https://laradock.io/ and works fine locally as well as on a test server.

How can I make this error 500 on posting the image become more useful so I can debug this issue? Is there a way to get a more useful error message using Nginx than error 500? Can PHP-FPM send over some more details somehow?