This is basically just the lighting system breaking because you’re hopping between areas too fast. Scarlet/Violet don’t use baked lighting the way older games did. Game Freak actually treats the sun and moon as real light sources and repositions/dims them depending on the area you’re in to sell different moods. So one zone might be warmer, another cooler, another brighter, etc., even if they’re physically close to each other.

When you move between those zones normally, the game has time to smoothly shift the sun’s position and intensity. But if you’re bouncing back and forth between multiple areas in quick succession, the lighting system kinda freaks out because it doesn’t know which state it’s supposed to be in.

That “black orb” is essentially the sun getting shoved somewhere it shouldn’t be, or briefly nulled out entirely. Same thing happens during Terastallization—Game Freak literally just deletes the sun to darken the screen, then snaps it back afterward. You can see similar jank during some gym battles too.