Noteworthy steps in chronological order:

1. User 1 creates a new world on Computer A.
2. User 1 clicks "Open to LAN" on Computer A.
3. User 2 starts Minecraft on Computer B and User 3 starts Minecraft on Computer C. Both of them enter the LAN world hosted on Computer A.
Note: Computers A and B are both connected to a single router using Ethernet; Computer C is connected to the same router through WiFi.
4. All three users play Minecraft on the LAN world for several hours across several different sessions over 3 days.
5. At a certain point in time immediately before the following steps, all three players are logged out.
6. User 3 logs into Minecraft on Computer A, then enters the world that all 3 users have been playing over LAN.
7. User 3 finds that their character is not in the correct location and does not have the correct items. Instead, User 3 finds that their character is in the last location occupied by User 1 and has the same items as those last carried by User 1.
8. User 3 logs out.
9. User 1 logs in to Computer A and starts up the LAN world. User 1 is in the correct location with the correct items.
10. User 3 logs in to Computer B and enters the LAN world.
11. User 3 is in the same incorrect location with incorrect items.
12. User 3 logs out.
13. User 3 logs in to Computer C and enters the LAN world.
14. User 3 is still in the same incorrect location with incorrect items.
15. User 3 logs out.
16. User 3 submits this bug report.