An 'Error_for_autosell_for_town_id_67:_bad_town_on_merchant_was_missing' error code occurred after talking to Ataman Omelian Kassap and leaving Serin Castle.

and If you talk to them near Vinica, the Nihonian mercenaries will disappear, and there will be no street battles.
(at wiki, Revolution in VInica step 8)

How can I fix this bug? and When do you fix this bug?