E203 - initial_scroll_position must be >= 0

Cause

A slide's initial_scroll_position: is negative. The field controls where the scrollbar starts on first display and must be a non-negative scroll offset.

Example

{ title: "T", elements: [...], initial_scroll_position: -10 }

How to fix

Use 0 (start at the top) or a positive value within [0, scroll_range].