Detect wrong inflection of custom words

I want to add a bunch of special Names to my (german) dictionary. Let’s say, there is a thing, called Tanmatra, it’s genitive is Tanmatras. I add both to LanguageTool-6.5-stable/org/languagetool/resource/de/hunspell/spelling_custom.txt and don’t get spelling errors on it.

But the does not check on proper inflection yet. So i added the following to LanguageTool-6.5-stable/org/languagetool/resource/de/added_custom.txt

Tanmatra Tanmatra EIG:NOM:SIN:NEU:ART:PER
Tanmatra Tanmatra EIG:DAT:SIN:NEU:ART:PER
Tanmatra Tanmatra EIG:AKK:SIN:NEU:ART:PER
Tanmatras Tanmatra EIG:GEN:SIN:NEU:ART:PER

When I run LT with -v i see that those Tags are correctly applied to the word Tanmatra in my testfile:

Er war sich des Tanmatra bewusst.

<S> Er[ich/PRO:PER:NOM:SIN:MAS,O] war[sein/VER:3:SIN:PRT:NON,sein/VER:AUX:1:SIN:PRT,sein/VER:AUX:3:SIN:PRT,O] sich[sich/PRO:REF:AKK:PLU:ALG,sich/PRO:REF:AKK:SIN:ALG,sich/PRO:REF:DAT:PLU:ALG,sich/PRO:REF:DAT:SIN:ALG,O] des[der/ART:DEF:GEN:SIN:MAS,der/ART:DEF:GEN:SIN:NEU,B-NP|NPS] Tanmatra[Tanmatra/EIG:NOM:SIN:NEU:ART:PER,Tanmatra/EIG:DAT:SIN:NEU:ART:PER,Tanmatra/EIG:AKK:SIN:NEU:ART:PER,I-NP|NPS] bewusst[bewusst/ADJ:PRD:GRU,O].[./PKT,<P/>,O]

But the grammar mistake is not recognized (genitive should be used here). What am i missing?

Could you try with a noun that’s not a proper noun, i.e. not using EIG? This might make a difference. I.e. as a test, just try to treat Tanmatra not as a proper noun.

That works! Thank you so much!