What causes this filling in of shadow with ambient occlusion?

[brazen cobalt]

Here's a clip, when the character turns to the left if you look along the top center of the video at the ceiling, the shadow kind of fills in along as the character turns.

https://streamable.com/ziduzi

I've tried toying around with the SSAO settings in the renderer data asset, lowering the intensity makes it less noticeable but then affects the general look of everything else. Anything I can do to improve the look without having to modify the SSAO settings for the whole game because of what's happening at the edge of the screen?

[primal osprey]

SSAO can only cast shadows from what's drawn on screen

Technical solutions would include "overscanning" to render pixels outside the visible area also, which I think used to be a built-in feature but now would require modifying the renderer in some way (or outside of that possibly doable by rendering through an RT camera to an Image)
It's pretty expensive though, so a preferred alternative could be to fade out the SSAO gradually near screen edges, though I don't think that's supported out of the box either

The issue is not all that glaring to a casual viewer in this case, so all you might need to do is change how that particular edge appears on screen
Bringing it lower more into view could be all that's needed to make the "filling" effect become unnoticeable