This project requires precision to work consistently. Here are my troubleshooting tips that I discovered while tinkering and developing this project plan:

The axles for the glide wheels bumps into the drop channel beams.

Trim the axle until it is flush with the wheels. If the washers start falling off, rub a little bit of hot glue on the outside of the axle and the washer to keep them in place.

Reposition the drop channel beams further apart.

The counterweight hits the glide rails while falling down.

Make sure the glide rails do not intersect the drop channel at all.

Make the drop channel gap slightly wider.

The throwing arm hits the drop channel.

Make sure the throwing arm rests between the glide rails before launch as shown in the image above.

Reposition the drop channel beams further apart.