Duplication Bug?

Multiplayer with 2 players entering fresh swamp gauntlet from respite, we kill boss, travel home. I receive a chest with "lost items" on Lodestar containing 2 Items out of my followers inventory. We made a new swamp, same procedure, we travel back. I get another chest (this time the same items but each twice and 1 other new item (5 total)).
(just did it again, another chest, just traveled there and back. I did interact with my followers inventory, maybe something to do with that (see screenshot)