I am not sure if i can call this a bug but don't think it is feature, so there it goes.
First off, i know the fact that we individually can only defeat one wave of the robber camp and therefore not able to attack when we defeat one wave.
However, when we send our troops to a robber camp we cannot launch another attack on the same robber camp (we get "Your troops are already on their way there" message) until our first attack reaches its destination, despite the fact that we have not defeated any robbers in the camp yet.
I see that the intention is not to let a player fight more than one wave but i think it could have been implemented better because it unnecessarily blocks the player to use the strategy of separately and simultaneously sending the hero to clear the camp and normal units to carry resources.
My proposed better implementation is just returning the second attack if the first attack successfully defeats the wave but obviously, i don't know the code so this may not be possible to implement.
Anyways, that's enough for my 4 chivalrous legos who lost their lives defeating the robbers. Cheers:)