The bug

A room that can generate in woodland mansions contains a chest which contains dark oak saplings, which are messily strewn about inside the chest as is standard for most loot chests. The issue here is that that pattern of dark oak saplings will always be the same for every such chest across different instances of that same room.

How to reproduce

1. Locate one of these chests or use a structure block to load the room:

   /setblock ~ ~ ~ structure_block{mode:"LOAD", name:"woodland_mansion/1x2_a4",showboundingbox:1}
   

2. Open the chest
3. Take a close note of the exact positions and counts of each item
4. Locate another of these chests
5. Note the counts and positions in this chest

Expected results

As this is a chest intended to contain randomly-placed items (unlike the chest found in the "fake end portal" room), the positions and counts would be random for each chest.

Actual results

The counts and positions match for every single chest of this type.