Event 5520 "A mongol ruler has raided one of our border provinces!" not working?

[Reveilled]

I'm currently holding the mongols at the borders of Georgia and Transoxiana, and then this event fires, setting the prosperity in Basra to struggling.

I'm pretty sure Basra doesn't border Russia, and since its trade links are all with provinces I own, I'm at a loss as to how this would happen.

 

[unmerged(11427)]

Well, this might be a long shot, but judging by the trigger conditions you don't have to border Golden Horde directly. You could be bordering their vassal. I know that GH rarely has vassals, but that's the only thing I could think of.

 

[Reveilled]

Well, this might be a long shot, but judging by the trigger conditions you don't have to border Golden Horde directly. You could be bordering their vassal. I know that GH rarely has vassals, but that's the only thing I could think of.

Nope. I border the golden Horde directly, but not at Basra.