A portion of a reference file attachment has missing elements, a portion of them are not displayed. It is 3d file and when opened this file as master and all the elements are intact and displayed correctly.
Reference file named "ref1.dgn" has elements of the model drawn at different Z depth. please see image (error different Z depth in 3D.jpg). Rotate the view to Front View, then zoomed in to the model and you will notice.
Open the reference file ref1.dgn and export it to 2D. To do this, go to File and Export to 2D (Save as 3D to 2D) and named it asref2.dgn Please see image (ref new file). see as attached. Subsequently, reference attached it to A.dgn.
Result : Open active file A.dgn and you will see the new reference attachment “ref2.dgn” is now showing the full model and is corrected.