Problem with theming? CPU bound httpd

Nextcloud version: 13.0.4
Operating system and version: OpenSuse Leap 42.3
Apache or nginx version: Apache 2.4.23
PHP version: 7.0.7

The issue you are facing:

If I enable theming in the apps section, then some time after a browser login one or more httpd processes will become CPU bound. The number of such processes increases over time.

If I disable theming, this does not happen.

Is this the first time you’ve seen this error? (Y/N):

Steps to replicate it:

  1. Enable all apps (except encryption in my case)
  2. Log in with browser, go to various apps (usually gallery and files is sufficient).
  3. Maybe login/logout and repeat if problem has not occurred yet.

The output of your Nextcloud log in Admin > Logging:

No errors.

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

  'instanceid' => '<stuff>',
  'passwordsalt' => '<stuff>',
  'secret' => '<stuff>/qAm+tUy1M4mfUwX5aF',
  'trusted_domains' =>
  array (
    0 => '<stuff>',
    1 => <stuff>',
   ...
    5 => '<stuff>',
  ),
  'datadirectory' => '<stuff>',
  'overwrite.cli.url' => '<stuff>',
  'dbtype' => 'sqlite3',
  'version' => '13.0.4.0',
  'logtimezone' => 'UTC',
  'installed' => true,
  'mail_smtpmode' => 'smtp',
  'mail_from_address' => '<stuff>',
  'mail_domain' => '<stuff>',
  'mail_smtphost' => '<stuff>',
  'theme' => '',
  'maintenance' => false,
  'loglevel' => 1,
  'trashbin_retention_obligation' => 'auto',
  'updatechecker' => false,
  'updater.secret' => '<stuff>',
  'memcache.local' => '\\OC\\Memcache\\Redis',
  'redis' =>
  array (
    'host' => 'localhost',
    'port' => 6379,
  ),
  'memcache.locking' => '\\OC\\Memcache\\Redis',
  'ldapIgnoreNamingRules' => false,
  'ldapProviderFactory' => '\\OCA\\User_LDAP\\LDAPProviderFactory',

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

These lines repeated every few seconds (same as always):

==> /var/log/apache2/ssl_request_log <==
[21/Jun/2018:13:08:13 +1000] x.y.z.t TLSv1.2 “PROPFIND /remote.php/dav/files// HTTP/1.1” 364 “-” “Mozilla/5.0 (Windows) mirall/2.4.1 (build 9270)”

==> /var/log/apache2/access_log <==
<x.y.z.t> - [21/Jun/2018:13:08:13 +1000] “GET /ocs/v2.php/apps/notifications/api/v1/notifications?format=json HTTP/1.1” 200 74