Can only upload very small files

Nextcloud version 13.0.5 (Also on 13.0.4)
CoreOS Docker Image (latest)

The issue you are facing:

Is this the first time you’ve seen this error? Y

Steps to replicate it:

  1. Log in
  2. Upload a “large” file (50MB) (however a file a few KBs works fine)
  3. Upload screen get’s stuck at “A few seconds”

The output of your Nextcloud log in Admin > Logging:

No fatal or errors, only debug info

The output of your config.php file in /path/to/nextcloud (make sure you remove any identifiable information!):

$CONFIG = array (
  'instanceid' => '',
  'passwordsalt' => '',
  'secret' => '',
  'trusted_domains' =>
  array (

  ),
  'datadirectory' => '/var/www/html/data',
  'overwrite.cli.url' => '',
  'dbtype' => 'mysql',
  'version' => '13.0.5.2',
  'dbname' => 'nextcloud',
  'dbhost' => '',
  'dbport' => '3306',
  'dbtableprefix' => 'oc_',
  'dbuser' => '',
  'dbpassword' => '',
  'installed' => true,
  'ldapIgnoreNamingRules' => false,
  'ldapProviderFactory' => '\\OCA\\User_LDAP\\LDAPProviderFactory',
  'mail_smtpmode' => 'smtp',
  'mail_smtpauthtype' => 'LOGIN',
  'mail_from_address' => '',
  'mail_domain' => 'gmail.com',
  'mail_smtphost' => 'smtp.gmail.com',
  'mail_smtpport' => '465',
  'mail_smtpauth' => 1,
  'mail_smtpname' => '',
  'mail_smtppassword' => '',
  'mail_smtpsecure' => 'ssl',
  'updater.release.channel' => 'stable',
  'loglevel' => 0,
  'maintenance' => false,
  'filelocking.enabled' => false,
  'theme' => '',
  'memcache.local' => '\\OC\\Memcache\\APCu',
  'lost_password_link' => '',
  'htaccess.RewriteBase' => '/',
  'apps_paths' =>
  array (
    0 =>
    array (
      'path' => '/var/www/html/apps',
      'url' => '/apps',
      'writable' => false,
    ),
    1 =>
    array (
      'path' => '/var/www/html/custom_apps',
      'url' => '/custom_apps',
      'writable' => true,
    ),
  ),
);

The output of your Apache/nginx/system log in /var/log/____:

When I try to nano/vim these files inside the docker container they report: "This is not a file".  ls -l shows that they appear to be symlinks to /dev/stdout

Solved!

Turns out this wasnt an issue with Nextcloud, but my NGINX proxy.

I edited the file:
./etc/nginx/vhost.d/default
and added
client_max_body_size 20G;