I've had this on several occasions since 0.53 hit stable.
Using a pristine (or worn) TTsKO jacket in combination with a Smersh vest + backpack. When a random zombie hits you once, the jacket is ruined but the contents are fine some of the times.
I thought this was a one time bug, but it's been happening multiple times in a row (not only with a TTsKO jacket but others as well).