They appear to indicate a library part that is not loaded. Given that this appears in association with the doors. I would suspect that is it a door label that is not present in your loaded libraries. Take a look at your library report, it should indicate if a used part is not loaded. If that is the case, locate the part and loaded with the library manager.
HTH
Erich
AC 19 6006 & AC 20
Mac OS 10.11.5
15" Retina MacBook Pro 2.6
27" iMac Retina 5K