The reason I know is, of course, that I have done the same and been equally frustrated. A gps-track software (gpstm) has a wonderful function: select duplicate elements (with co-ordinates to within a pre-defined distance). Very useful for those accidental duplications.

BTW, now that I am enlightened as to the meaning of ébrasement, I sent you a simpler workaround model for the ébrasement opening by e-mail. It should work as long as you can tweak the inner wall texture and fill it with a window without cut-out (so it does not interfere).

ok