I had this exact same issue. I read in another post that for a sphere trace the start and end location need to be different in order to properly detect the impact point.
I tried by using the same location but added 0.001 offset in the z direction for the start vector and it started properly detecting the impact point.
This was not an issue until UE 4.27. When I migrated my project to UE5, I started having this issue. Not sure if it is a bug or an enhancement.
For more info check this post: impact Point location on trace ?