This is still happening with patch 1.02. Clothing damage is pointless now since you just have to settle with ruined items. I've noticed that it takes a bit if it's pristine but after the first repair when in a damaged or badly damaged state, takes nothing to destroy them after. It's constant repair with no way to keep up.

It happens when the equipped gun is minimized (showing what can be added to the gun ie clip, silencer, etc) in the inventory screen. When you open it up again you are able to access the jeans and backpack.

Can access while equipped if you get to the backpack and jeans using up instead of down.

Happen again with no new item pickup, but after fighting a zombie which caused bleeding. Found it while trying to bandage and unable to access jeans or backpack while equipped. Seems to be random.