Intersect is unreliable

I’m working on a plugin where one of the steps involve boolean operations.

The thing is that intersecting two shapes rarely work.

What’s going in here, why isn’t there showing up any two shapes when they clearly overlap?

I wasn’t allowed to share the screen recording, so I uploaded it to my site here:
https://tcarisland.no/wp-content/uploads/2024/02/IntersectBug.mov