explanation:
an entity has for example an inventory container with 500 slots, put the items after 256th slot, exit world and enter again, these items will move to the first 256 slots overwriting items in these slots after reloading the world or retrieving the entity from a structure.

https://streamable.com/biyxb6
in the attached video i have a custom entity with big inventory size any item stored after 256th are moved back as shown in the video