Filtering calendar by multiple timeranges strange behaviour

*For now I have to put this on hold and dive into it deeper next week. the reproduction of this model works and I probably didnt give enough information to solve this problem. 
**fyi: the connection in Kalender--Einstellungen is inactive and there is another table connected to Bewerbungen which also connects to 'Kalender' (with an active relation). A measure does DISTINCTCOUNT'Einstellungen' with USERELATIONSHIP

Hey guys, I have a calendar which gets filtered by another table 'Zeitraum Filter'. This table contains multiple dateranges for visual filtering purposes in column 'Filter' i.e. ( "2023", "Q1+Q2", "Mid22-Mid23" ... ) with its coresponding dates in "Date" column
(*<>1)

The calendar then filters 'Einstellungen' for the remaining dates in 'Kalender'

It works fine and I can filter 'Einstellungen' with all of those timeranges. The problem lies within 'Bewerbungen'. It has a category column I want to use to filter 'Einstellungen' even further.

Goal should be a visual with activ filters: "Zeitraum Filter"[Filter] = "Q1+Q2" & Bewerbungen[Empf.K] = "Y" showing only those entries in 'Einstellungen'

For some reason it works when I use 2023, 2022 ... but as soon as I use one of the "special" timeframes it shows no data. I cant grasp why it works for one but not for the others, they shouldnt be any different but other dates

Thanks for your help