https://imgur.com/a/qw0R5qU

This could be because the XYZ coordinates were mixed up, as the item will always travel the height of the belt, but in the Z direction instead of the Y direction. (Please ignore the message about the calculator, it is from a different mod.)

All the belts are in one chunk.

Vertical belts were never meant to transport items in the first place.
This issue has been addressed in 0.2.3. Thanks for the report and feel free to re-open if need be.