You can open 2 item containers at the same time And if you do 2 containers only one will be closed.

Link to video: https://1drv.ms/v/s!AmvLr9BXZXk7glOkwvYCMy3Gx7yh?e=zVLbbk

Steps to reproduce (watching the video is better than my trash explanation)

1. Place two shulker boxes next to themselves
2. Run/fly sideways right clicking fast staring at the shulker boxes
3. You now opened 2 shulker boxes

Expected results:
You shouldn't be able to open two containers at the same time

Observed results:
You open 2 shulker boxes and if you press the x one of them stays open