Miss Fisher refers to the Slavic language spoken at the docks, yet Latvian is not a Slavic language; it belongs to the Baltic branch of the Indo-European language family. The names of the Latvian characters don't follow Latvian naming conventions, either, being rather generically Slavic Eastern European - suggesting the writers/makers indeed did not research Latvian culture properly.
When Dot shows Miss Fisher a newspaper from the 1920s, the "filler" story below the headline is about the acquittal of Casey Anthony from 2011.