The Federal Intelligence Service (Bundesnachrichtendienst, BND) has no domestic jurisdiction. Neither would the agency sift through an apartment or arrest and tell a person, esp. not a critical journalist, that it does so. Nor would it use immigration law to intimidate a critic because it would be more effective to have the Aliens Department do it.
When Quinn picks up his second target at the post office, the sign (which reads "Deutsche Post" (German Post) in no way resembles those used by Deutsche Post DHL Group.
The ringing sound you here in all of the phone calls which are made in the whole season are wrong. The German ringing (and waiting) sound has regular intervals, a different tone and each sound is longer in general.
The invitation by Hezbollah for the During Foundation to visit the refugee camp, as depicted in the "previously on Homeland", had not happened previously in the previous show "Separation Anxiety".