If you get two backpacks from sophisticated backpacks and fill one up, the other one also fills up with the same stuff when you place them down. This goes for the upgrades as well. It's also possible to delete the items, though I don't know exactly how to replicate that. When I was "testing", as I had just made two, I had made two sets of upgrades and noticed that both of my gold backpacks had gotten the upgrade when I had only put one set in.

This can only really happen if you have two backpacks that have the same UUID - could you check advanced tooltip (F3 + h) of those two backpacks and check what UUID they have? if they have the same one to fix I will need to understand how exactly you have obtained those backpacks because the only way I know of to get the duplicate UUID is by duplicating the already open once backpack in creative mode.

I simply crafted the backpacks in survival. They have the same UUID. Maybe I had a lag spike that I didn't notice and it created a problem. The exact story for the backpacks is that I made one at the start of a rougelike dungeon. I went down several floors and upgraded it to gold around floor 3 after climbing back up. After I had finished floor 4 I went back up and made a second gold one and upgrades for both. When I tried to put in the upgrades for the new backpack, I already had some in there.

I've tried several times to recreate what I did when I made the second backpack, to no success. The only thing I have noticed is that when I move the unopened backpack around in my inventory, the UUID changes, so possibly during a lag spike that I didn't notice something might have happened? When I first made the backpacks, I accidentally tried to switch the two in my inventory when I was putting the upgrades in. That is my best guess on when this happened.

Actually I can see what's happening here. Something in ATM7 is making backpacks in JEI / recipes act as if they were already open by player and got UUID assigned - you should not be able to see UUID for any backpack in JEI or in recipe results when you shift over them. I will need to somehow figure out what is causing that and if there's a way for me to prevent it. Any help narrowing down what mod that is would be great.

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

This was fixed in one of the last sophisticated backpacks releases by an addition of custom recipe that deletes UUID from backpack that was just crafted. So you should be able to just close the issue

This was fixed in one of the last sophisticated backpacks releases by an addition of custom recipe that deletes UUID from backpack that was just crafted. So you should be able to just close the issue

excellent, well the stale bot beat us to it, but good to know
also this is a nice feature

Added config that allows disabling opening another player's backpack on their back globally for everyone on the server