The problem was solved like this (another "crutch"):
In the file cfgIgnoreList.xml there are 2 lines like this:
<type name="Watchtower" cheatCheck="1"></type>
<type name="Fence" cheatCheck="1"></type>
deleting these lines solves the problem. but! If you started the server and there were no buildings, then they will not appear. Because the server started without any buildings and recorded this information in its files. So I had to take the mission files from the backup.

I have exactly the same problem. All the buildings of the players have disappeared. Backups could not solve the problem. I don't understand what the problem might be...