Posted by Gary S on Mar 30, 2021; 12:35am
URL: https://forum.librecad.org/Librecad-keeps-adding-blocks-to-block-list-tp5715315p5720489.html

BTW, I also note in the drawing "shop-south_roofing-only_2021-03-28.dxf" all the layers are locked.  When you mention "since the other quirk of LibreCAD is that very large files will not permit selection of an object. ".  Check the drawing you have as locked layers will also prevent selecting an object.