I've experienced this myself, and now I've heard of other users having it happen to them (most notably Thirdkid and Smitedyou1 who lost 2 melon swords today).

My story: after a rollback, I have had these things happen:

Situation 1:

Stuff I had before rollback: Eff5 Unb3 For3 Dpick and Eff5 Unb3 Silk1 Dpick

Stuff I had after rollback: 2 (two) Eff5 Unb3 Silk1 Dpicks

Basically my For3 got deleted and my Silk got duped.

Situation 2:

Stuff I had before rollback: Eff4 Unb3 Shovel and Eff5 Unb3 Silk1 Shovel
Stuff I had after rollback: 2 (two) Eff5 Unb3 Silk1 Shovels

Basically the Eff4 Unb3 got lost and the Eff5 Silk got duped.


In both cases I had recently swapped out a worn out tool for a fresh one from my chest in my town of SanFrancisco (no residents except myself). This town is almost always inactive chunks because no one is nearby. Both times I had been in a populated area like spawn or the marketplace at the time of the rollback.

To me, it seems that players and active chunks are rolled back, but not inactive chunks. Thus, if I take something from a chest in SanFrancisco, then I go to the marketplace, then a rollback happens, I won't have that item and the item won't be in my chest in SanFrancisco either -- I was rolled back, but SanFrancisco WASN'T.

Duping can happen similarly. If I have an item on me and I put it into the chest in SanFrancisco, then I go to the market, then there's a rollback -- I will have the item still AND the chest in SanFrancisco will have the item because once again, I am rolled back but the inactive chunks in my city are not.

This is my theory for the problem.