I stationed some troops in the town of an alliance member.
Then I pillaged an inactive player on the same island.
Attack was successful and everything was loaded and moved back to the town of origin.
Upon arrival of the goods in the intermediate town (the alliance member), the troops scattered and the pillaged goods were lost:
This happened to me and two of my fellow alliance members. The port was never occupied nor attacked by another player.
Only one speed boat was stationed in the port of this alliance member.
To my understanding of the mechanics, the scattering shouldn't have happened. So I'm suspecting this is a bug.