What major drawback forced extensive retrofitting of conventional palletizers?

Switching case size or adopting a new stacking pattern.

Conventional palletizers, also known as layer-type palletizers, were inherently inflexible because they were designed only for a specific product size and fixed stacking pattern. If a company needed to change production to a different case dimension or implement a new, potentially more space-efficient arrangement, the entire machine usually required costly, extensive retrofitting or complete replacement. This lack of adaptability made them unsuitable for environments with increasing product diversity, unlike later robotic solutions.