When I swing very slowly, maybe at 20% of my normal speed, the swing looks amazing. It's perfectly shallow. When I go to normal speed, it gets too steep. Why could that be, and how get my normal swing to look like the slow one?
When you swing slowly, you probably have more time to maintain a shallow path. Try to focus on maintaining that same feel and technique but at a faster pace. Practicing with a metronome or using drills like swinging with a pause at the top can help you build that consistency.