"something is about to happen"

[LittleMorgan]

Strange thing, I was in Port Royal on Jamaica doing some shopping and drinking and every time I tried to fast travel to some city location my travels were interrupted, I was placed directly outside the location I tried to leave and got this message.
I search the whole city but nothing unusual happened.
What's this?

 

[Bismarck]

When I find a treasure, I usually can't fast travel (with the message: something is going to happen) because some thugs want to have a share of it.
Well, they did get some metal from me, but it wasn't gold or silver.
After their dead, fast travel works again.