I have a daily cronjob with runJobs.php, but that doesn't fix the problem. I enabled debugging.
I paste a part of my debug.log here showing the relevant request. Maybe somebody sees an error?
I searched the whole file for "error" but only found something like "SMW\SQLStore\Lookup\ErrorLookup::fetchFromTable (for SMW\Indicator\EntityExaminerIndicators\ConstraintErrorEntityExaminerIndicatorProvider::findErrors)..."
Start request GET /mediawiki/index.php?target=http%3A%2F%2Fwww.integralesleben.org%2Fde%2Fil-home%2Fil-integrales-leben%2Fgrundlagen-des-integralen%2Flinien-der-entwicklung%2Fspiral-dynamics%2F&namespace=&title=Spezial%3AWeblinksuche
IP: ...
HTTP HEADERS:
HOST: secret-wiki.de
...
[DBReplication] Wikimedia\Rdbms\ChronologyProtector::getStartupMasterPositions: client ID is 9ed5874d1324e84585f21fd2e9d54985 (read)
[DBReplication] Wikimedia\Rdbms\ChronologyProtector::getStartupMasterPositions: key is global:Wikimedia\Rdbms\ChronologyProtector:9ed5874d1324e84585f21fd2e9d54985:v2 (read)
[DBConnection] Wikimedia\Rdbms\LoadBalancer::lazyLoadReplicationPositions: executed chronology callback.
[DBConnection] Wikimedia\Rdbms\LoadBalancer::getLocalConnection: opened new connection for 0
[DBQuery] Wikimedia\Rdbms\DatabaseMysqlBase::serverIsReadOnly [0.001s] someserver.com: SELECT @@GLOBAL.read_only AS Value
[DBQuery] Wikimedia\Rdbms\Database::beginIfImplied (LCStoreDB::get) [0s] someserver.com: BEGIN
[DBQuery] LCStoreDB::get [0.007s] someserver.com: SELECT lc_value FROM `l10n_cache` WHERE lc_lang = 'de' AND lc_key = 'deps' LIMIT 1
[DBQuery] LCStoreDB::get [0.017s] someserver.com: SELECT lc_value FROM `l10n_cache` WHERE lc_lang = 'de' AND lc_key = 'list' LIMIT 1
[DBQuery] LCStoreDB::get [0.005s] someserver.com: SELECT lc_value FROM `l10n_cache` WHERE lc_lang = 'de' AND lc_key = 'preload' LIMIT 1
[DBQuery] LCStoreDB::get [0.001s] someserver.com: SELECT lc_value FROM `l10n_cache` WHERE lc_lang = 'de' AND lc_key = 'preload' LIMIT 1
[DBQuery] LCStoreDB::get [0.001s] someserver.com: SELECT lc_value FROM `l10n_cache` WHERE lc_lang = 'de' AND lc_key = 'fallbackSequence' LIMIT 1
[session] SessionManager using store SqlBagOStuff
[DBQuery] Wikimedia\Rdbms\DatabaseMysqlBase::open [0.005s] someserver.com: SET group_concat_max_len = 262144, sql_mode = ''
[DBConnection] Wikimedia\Rdbms\LoadBalancer::getLocalConnection: opened new connection for 0
[DBQuery] SqlBagOStuff::fetchBlobMulti [0.001s] someserver.com: SELECT keyname,value,exptime FROM `objectcache` WHERE keyname = 'usr_p408127_5:MWSession:f449lgrt544njp76kf780vk586mf6ddl'
[DBQuery] LCStoreDB::get [0.004s] someserver.com: SELECT lc_value FROM `l10n_cache` WHERE lc_lang = 'de' AND lc_key = 'namespaceAliases' LIMIT 1
[DBQuery] LCStoreDB::get [0s] someserver.com: SELECT lc_value FROM `l10n_cache` WHERE lc_lang = 'de' AND lc_key = 'namespaceGenderAliases' LIMIT 1
[DBQuery] LCStoreDB::get [0.001s] someserver.com: SELECT lc_value FROM `l10n_cache` WHERE lc_lang = 'de' AND lc_key = 'specialPageAliases' LIMIT 1
[UserOptionsManager] Loading options from database
[DBQuery] MediaWiki\User\UserOptionsManager::loadUserOptions [0.001s] someserver.com: SELECT up_property,up_value FROM `user_properties` WHERE up_user = 1
[MessageCache] MessageCache using store APCUBagOStuff
[MessageCache] MessageCache::load: Loading de... local cache is empty, got from global cache
[DBQuery] LCStoreDB::get [0.007s] someserver.com: SELECT lc_value FROM `l10n_cache` WHERE lc_lang = 'de' AND lc_key = 'messages:linksearch' LIMIT 1
ParserFactory: using default preprocessor
[DBQuery] LCStoreDB::get [0.001s] someserver.com: SELECT lc_value FROM `l10n_cache` WHERE lc_lang = 'de' AND lc_key = 'magicWords' LIMIT 1
Unstubbing $wgLang on call of $wgLang::unstub from ParserOptions->__construct
[DBQuery] LCStoreDB::get [0.005s] someserver.com: SELECT lc_value FROM `l10n_cache` WHERE lc_lang = 'de' AND lc_key = 'messages:linksearch-summary' LIMIT 1
[DBQuery] LCStoreDB::get [0.003s] someserver.com: SELECT lc_value FROM `l10n_cache` WHERE lc_lang = 'de' AND lc_key = 'messages:linksearch-text' LIMIT 1
[DBQuery] LCStoreDB::get [0.008s] someserver.com: SELECT lc_value FROM `l10n_cache` WHERE lc_lang = 'de' AND lc_key = 'digitTransformTable' LIMIT 1
[DBQuery] LCStoreDB::get [0.002s] someserver.com: SELECT lc_value FROM `l10n_cache` WHERE lc_lang = 'de' AND lc_key = 'separatorTransformTable' LIMIT 1
[DBQuery] LCStoreDB::get [0.001s] someserver.com: SELECT lc_value FROM `l10n_cache` WHERE lc_lang = 'de' AND lc_key = 'compiledPluralRules' LIMIT 1
[DBQuery] LCStoreDB::get [0.008s] someserver.com: SELECT lc_value FROM `l10n_cache` WHERE lc_lang = 'de' AND lc_key = 'linkPrefixExtension' LIMIT 1
[DBQuery] LCStoreDB::get [0.002s] someserver.com: SELECT lc_value FROM `l10n_cache` WHERE lc_lang = 'de' AND lc_key = 'messages:linksearch-pat' LIMIT 1
[DBQuery] LCStoreDB::get [0.005s] someserver.com: SELECT lc_value FROM `l10n_cache` WHERE lc_lang = 'de' AND lc_key = 'messages:linksearch-ns' LIMIT 1
[DBQuery] LCStoreDB::get [0.002s] someserver.com: SELECT lc_value FROM `l10n_cache` WHERE lc_lang = 'de' AND lc_key = 'rtl' LIMIT 1
[DBQuery] LCStoreDB::get [0.001s] someserver.com: SELECT lc_value FROM `l10n_cache` WHERE lc_lang = 'de' AND lc_key = 'messages:linksearch-ok' LIMIT 1
[DBQuery] LCStoreDB::get [0.008s] someserver.com: SELECT lc_value FROM `l10n_cache` WHERE lc_lang = 'de' AND lc_key = 'messages:namespacesall' LIMIT 1
[DBQuery] LCStoreDB::get [0.002s] someserver.com: SELECT lc_value FROM `l10n_cache` WHERE lc_lang = 'de' AND lc_key = 'messages:blanknamespace' LIMIT 1
[DBQuery] LCStoreDB::get [0.005s] someserver.com: SELECT lc_value FROM `l10n_cache` WHERE lc_lang = 'de' AND lc_key = 'messages:linksearch-helppage' LIMIT 1
[MessageCache] MessageCache::load: Loading en... local cache is empty, got from global cache
[DBQuery] LCStoreDB::get [0.003s] someserver.com: SELECT lc_value FROM `l10n_cache` WHERE lc_lang = 'en' AND lc_key = 'deps' LIMIT 1
[DBQuery] LCStoreDB::get [0.026s] someserver.com: SELECT lc_value FROM `l10n_cache` WHERE lc_lang = 'en' AND lc_key = 'list' LIMIT 1
[DBQuery] LCStoreDB::get [0.002s] someserver.com: SELECT lc_value FROM `l10n_cache` WHERE lc_lang = 'en' AND lc_key = 'preload' LIMIT 1
[DBQuery] LCStoreDB::get [0.006s] someserver.com: SELECT lc_value FROM `l10n_cache` WHERE lc_lang = 'en' AND lc_key = 'preload' LIMIT 1
[DBQuery] LCStoreDB::get [0.002s] someserver.com: SELECT lc_value FROM `l10n_cache` WHERE lc_lang = 'en' AND lc_key = 'messages:linksearch-helppage' LIMIT 1
[DBQuery] LCStoreDB::get [0.001s] someserver.com: SELECT lc_value FROM `l10n_cache` WHERE lc_lang = 'de' AND lc_key = 'messages:helppage-top-gethelp' LIMIT 1
[DBQuery] SpecialLinkSearch::reallyDoQuery [0.011s] someserver.com: SELECT page_namespace AS `namespace`,page_title AS `title`,el_index AS `value`,el_to AS `url` FROM `page`,`externallinks` WHERE (page_id = el_from) AND el_index_60 = 'http://org.integralesleben.www./de/il-home/il-integrales-leb' AND (el_index LIKE 'http://org.integralesleben.www./de/il-home/il-integrales-leben/grundlagen-des-integralen/linien-der-entwicklung/spiral-dynamics/%' ESCAPE '`' ) ORDER BY el_index_60,el_id LIMIT 51
[DBQuery] LinkBatch::doQuery [0.011s] someserver.com: SELECT page_id,page_len,page_is_redirect,page_latest,page_restrictions,page_content_model,page_namespace,page_title FROM `page` WHERE (page_namespace = 0 AND page_title = 'Spiral_Dynamics')
[DBQuery] LCStoreDB::get [0.001s] someserver.com: SELECT lc_value FROM `l10n_cache` WHERE lc_lang = 'de' AND lc_key = 'messages:showingresultsinrange' LIMIT 1
[DBQuery] LCStoreDB::get [0.009s] someserver.com: SELECT lc_value FROM `l10n_cache` WHERE lc_lang = 'de' AND lc_key = 'digitGroupingPattern' LIMIT 1
[DBQuery] LCStoreDB::get [0.001s] someserver.com: SELECT lc_value FROM `l10n_cache` WHERE lc_lang = 'de' AND lc_key = 'minimumGroupingDigits' LIMIT 1
[DBQuery] LCStoreDB::get [0.001s] someserver.com: SELECT lc_value FROM `l10n_cache` WHERE lc_lang = 'de' AND lc_key = 'messages:prevn' LIMIT 1
[DBQuery] LCStoreDB::get [0.007s] someserver.com: SELECT lc_value FROM `l10n_cache` WHERE lc_lang = 'de' AND lc_key = 'messages:nextn' LIMIT 1
[DBQuery] LCStoreDB::get [0.002s] someserver.com: SELECT lc_value FROM `l10n_cache` WHERE lc_lang = 'de' AND lc_key = 'messages:shown-title' LIMIT 1
[DBQuery] LCStoreDB::get [0.004s] someserver.com: SELECT lc_value FROM `l10n_cache` WHERE lc_lang = 'de' AND lc_key = 'messages:pipe-separator' LIMIT 1
[DBQuery] LCStoreDB::get [0.005s] someserver.com: SELECT lc_value FROM `l10n_cache` WHERE lc_lang = 'de' AND lc_key = 'messages:viewprevnext' LIMIT 1
[DBQuery] LCStoreDB::get [0s] someserver.com: SELECT lc_value FROM `l10n_cache` WHERE lc_lang = 'de' AND lc_key = 'messages:linksearch-line' LIMIT 1
[DBQuery] MediaWiki::preOutputCommit [0s] someserver.com: COMMIT
MediaWiki::preOutputCommit: primary transaction round committed
MediaWiki::preOutputCommit: pre-send deferred updates completed
MediaWiki::preOutputCommit: session changes committed
[DBReplication] Wikimedia\Rdbms\ChronologyProtector::shutdown: no master positions to save
MediaWiki::preOutputCommit: LBFactory shutdown completed
OutputPage::haveCacheVaryCookies: found Secret_WikiToken
...