Factorio Forums

This is how it works:

Build large structure (using BP), someone else marks it for deconstruction and it gets partially deconstructed, then you place the blueprint right on top of it to rebuild what has been deconstructed before you remove all the left over "deconstruction marks". The new blueprint is placed but the deconstruction marks remain. You then remove the deconstruction marks with shift+decon but the robots keep trying to place a wall where it has already been placed.

Hope that is not too confusing. Can provide additional data if needed.

Yes, the way to prevent that is to not do that

Either that, or we don't allow placing ghosts over entities marked for deconstruction and that sounds like it would be far more annoying.