There's an issue that if the player has a trade route and a good in the route is boycotted in Europe, then wagons won't unload them in the city defined in the trade route.

I've been trying to find a patch or mod that someone has created that would fix this issue, but I haven't found one yet. Actually, I'm not sure if it's an error in a script or an error in the actual code for the game. If anyone finds anything that might be useful, please share.

Is the city setup to sell that good to Europe? Either through a custom house or sea trade? Havent a clue on this issue as I never heard of or seen it, but curious.

I don't think it's a bug. If the goods are boycotted, then you may not trade them with Europe or other players, only through the Custom House. That is the whole purpose of the Custom House.

It happens when using the trade routes between your own town. Try playing with the automation of trade routes and see what happens when you boycott something.

This is a bug that was present in the original game and that never was fixed.

The bug happens while having traderoutes defined between two 'new world' cities. If you are delivering, from one of your towns to another, any good that has been already boicotted in Europe, that good will stay in the transport (Caravan or ship) and you will have to do the delivery manually. If you don't the caravan/ship will continue the movement course of it's route keeping the good with it.

As I said at the begining, I don't know any fix for this issue.