Transparency above the right-hand map/chart on mobile looks a little odd

[dan-bowerman]

Description

Maps on Mobile - when scrolling through text, the map is not locked to the top and when user scrolls, they can see text above the map (messy looking)

Environment

• Any mobile browser

Screenshots

Steps to reproduce

1. Open any Storylines with a map or chart on the right (https://environmental-maps.canada.ca/RAMP-Storylines/index-ca-en.html#/en/1d11d1c0-8d99-404d-9e13-3135a4c8a196)
2. Scroll to map, the map is pinned at the top for that slide
3. Scroll some more, notice the "behind" contents appear above.

Expected behavior

I expect the map or chart to lock to the top so I cannot see text above the map that I have already read.