Hello Riccardo,
without knowing your implementation I can only make rudimentary assumptions:
1. In the slot method associated to the Vertical List's property OnLoadItem you have to adjust the size of the item to fit the size of the list. (See Implement the OnLoadItem slot method to load the items). The implementation of the slot method should end with a line similar to:
itemView.Bounds.size = VerticalList.ViewSize;
2. The component implementing the list item does not adjust its content when the component itself changes its size. Or it adjusts the content incorrectly. Assuming you have the item component filled entirely with a rectangle view and you want the component to adjust the size of the rectangle view so it continues filling the entire item, configure the views Layout property properly. (See the chapter Configuring component layout). For example:
I hope one of the ideas helps you further to fix the issue.
Best regards
Paul Banach