I've added the teutonic_knights_hq to Konigsberg (in descr_strat) so the Teutonic Order would be capable of recruiting some knights from the start of the late era game of SS 5.1.

To this end, I've added teutonic_order to the requires factions part in export_descr_buildings for the Teutonic guild and units respectively.
I've also added teutonic_order to the ownership and era parts in export_descr_unit.

Problem is, when I recruit Teutonic Knights or Dismounted Teutonic Knights their unit card looks like blackshirt peasants and on the battle map they become rider less horses and invisible knights.

Since they work fine when I recruit them as HRE, I must be doing something wrong/forgetting something regarding their model/unit cards. Does anyone know if there's an easy way to fix this?

I'd say that because the models/unit cards work for HRE, it should be just a matter of changing a certain text reference, but I can't find which file refers to the unit cards or any other way to do this.

Btw, the same applies to trying to add Dismounted Knights Hospitaller to Jerusalem.