Same carton, two orientations. The only thing that changed was which way it faced.
Long dimension forward. Spans many rollers, sits flat, rides stable.
Short dimension forward. Fewer rollers, so it teeters and its leading edge dips into the gap.
The rule underneath both: at least three rollers in contact, always.
The baseline. Rigid bottom, square corners, behaves the same way every time.
Rigid, but handles, lids, and flanges change where they touch the rollers.
No rigid bottom. Shape shifts under its own weight. Won't accumulate or scan flat.
Everything else is specialty handling. Tires, hanging garments, irregular items no L by W by H can pin down. Each one bends the whole system around it. The one thing you can't afford is to find it after the system is built.