[out:xml][timeout:3600]; ( way(1026757740)['wikipedia'='de:Wackelstein Loh']; ); (._;>;); out meta qt;//['wikipedia tag links to 404']
[out:xml][timeout:3600]; ( node(1744379936)['wikidata'='Q35993156']['wikipedia'='de:Schwarzenthal (Haidmühle)']; node(240129389)['wikidata'='Q32018069']['wikipedia'='de:Freyung']; node(302339663)['wikidata'='Q35926626']['wikipedia'='de:Frauenberg (Haidmühle)']; ); (._;>;); out meta qt;//['wikipedia wikidata mismatch']
[out:xml][timeout:3600]; ( node(1676613191)['wikidata'='Q37781560']['wikipedia'='de:Praßreut']; ); (._;>;); out meta qt;//['wikipedia wikidata mismatch - wikipedia points to disambiguation page and wikidata does not']
[out:xml][timeout:3600]; ( way(303530317)['architect:wikipedia'='Johann Baptist Schott']; ); (._;>;); out meta qt;//['malformed secondary wikipedia tag - for architect prefixed tags']
[out:xml][timeout:3600]; ( node(7972230710)['wikidata'='Q1623890']['wikipedia'='en:Hoher Filzberg']; ); (._;>;); out meta qt;//['wikipedia tag unexpected language']
JOSM Wikipedia plugin
Note to self: online version hosted at https://matkoniecz.github.io/OSM-wikipedia-tag-validator-reports, files are stored at https://github.com/matkoniecz/OSM-wikipedia-tag-validator-reports.