Hey, I didn't found this here. If it exists somewhere, please send me link and delete this.
So I kidnapped knocked out Pack Beast with full backpack on it's back from western hive caravan. Almost emptied the backpack with some spare robotic limbs, so I left the backpack on a carried the beast with me.
After few miles, I got into fight and was forced to drop the beast, so I took the backpack with robotic limbs into my char inventory and left the dead beast lying. After the fight ended, i put the backpack back on the dead beast and carried it with me. Then I realized, that inside the backack are the same things I looted from it once i kidnapped it. My new stored things dissapeard and the bag refreshed itself...