MakerBot Print is our newest print-prepration software, which supports native CAD files and STL assemblies,
allows you to interact with all your printers via the Cloud, and many other exciting new features.
I understand. It is done on purpose so the hobbed bolt will stay on its position held just by the filament - no need to secure it by nut on the other end. Deeper groove is better for this concept (like hyena hobbed bolt have). With shallow black bolts from China the simplest solution is to open the idler, help to guide the filament down to the hotend, than close idler and fix it by compression springs.
Hope it will help.