If alllanguages=true we duplicate the phrase of the query for each language because we might have language specific analyzers.
However we should explicitly add the language we search for to the query.
If we search for "bilder" and have languages de and en the calculated query currently is something like
The first part is for german (de-analyser shortens "bilder" to "bild") the second is for englisch.
As a result we also will find EN-Content that contains "bild". This is not wanted. We searched for "bilder".
We now explicitly add the language to this calculated internal query:
(allcontent:bild +LANGUAGE:de) (allcontent:bilder +LANGUAGE:en)