The issue seems to be in Top View. It consumes 10 times more memory than "Catalog Icons View" per run and never releases the resources. I have a hundred plain boxes which in "Catalog Icons" mode render real time on top, but take a minute or two to render in "Top View" mode. All are the same (cloned) and have the same color (no textures). The bottom (3D view) renders fine in both cases.