Items that I tell to build somewhere. But then are sold or upgraded before they are placed leave their ghost for ever in town.
Steps to reproduce:
Build 10 normal chairs and place them.
Before they are placed upgrade 10 chars to comfy chairs.
Another way to reproduce:
place 1 chair.
Then create task to move the 1 chair one place over.
Stop all units from doing work.
Have carpenter upgrade all 1 chair to comfy. now you have ghost chair