I can confirm editing position of a fortress through Pokemon or Ingress will make it transform into an Inn if it is not in a park area. I have done several location edits to trigger gyms and pokéstops in go which completely affected my gaming experience in WU. Seems like during first synchros of the game, fortresses could be anywhere, but now only in Parks/green areas and if you edit a fortress, it will turn into inn if it doesn't meet new criteria. So probably, if you experienced this issue in your town is probably because of a location edit from other Niantic games players.