Good morning, first off, what a great winter project! I'm really enjoying the assembly process so far!

I am confused with the installation of the J4 J5 retaining M4x10mm set screw. The manual states the two threaded holes line up when the "J5 motor mount is fully seated over the J4 main tube." Well, mine do line up, and when I thread the set screw in, it doesn't tighten up against anything, it just threads right on through, and falls out into the J4 tube. Both holes are threaded, so I'm not understanding where the "retention" occurs, cinching the two parts in place.

Thank you in advance for any clarification!