With the release of version 1.27, a change was introduced in cfgignorelist.xml:
<type name="Watchtower" cheatCheck="1"></type> <type name="Fence" cheatCheck="1"></type>
The intended purpose of this change is unclear, but it does not appear to be meant for despawning player-built structures on server resets. However, this is exactly what seems to be happening.
A player on my server first reported that their fences were disappearing shortly after being built or after a server reset. To verify this, I tested the change on my LAN server. After constructing a wall and restarting the server with the above modification in place, I logged back in to find that the wall had partially despawned, leaving only the upper frames.
I then repeated the process without cfgignorelist.xml change and found that the wall remained intact.
If this issue is not addressed, it could affect thousands of players, leading to widespread frustration.