The bug occurs with the object called the Traveller's Sack. The essence of the bug is that when removing the Traveller's Sack with character he appears in the slots in the backpack, which he himself also gives.
Thus, the slots received from the Traveller's Sack disappear with a Traveller's Sack and return impossible it if not to wear another.
I think the bug is quite serious and I hope that it will fix in the future.
P.S.| What would bug worked, you need to have a full backpack and to remove the bag holding the Shift button.
