I was testing trading with piglins, filled inventory up & had to lay down a shulker box to clear up space. I think this has something to do with piglins that are supposed to get aggressive towards players in bastions etc opening chests, maybe the player owned shulker box counts as a chest to them. To replicate: trade with some pig people till you have to use a shulker box to clear space. Set it on the ground right where you are trading,try to use it. Piglins will probably become aggressive.