For one of the item_display entities, enter the following in the “Additional NBT” input field:
"components": {"minecraft:banner_patterns": [{"color": "yellow", "pattern": "minecraft:gradient_up"}]}
Generate the command.

Examine the generated command. The "components" field is placed at the entity root level, for example:
{id:"minecraft:item_display", item:{id:"minecraft:green_banner",Count:1}, "components":{…}}
instead of being correctly nested inside the item object.

Execute the command in-game. The banner displays no gradient pattern because the item style is not read from an invalid root-level field.

Expected behavior:
The "components" field should be placed inside the item object, like:
item:{id:"minecraft:green_banner", count:1, components:{"minecraft:banner_patterns":[...]}}