Metaphorical movie with some apparent flaws (please change my mind)

Rating: 7/10 (16 February 2020)

I actually fast forwarded the movie after climax. Still can't fathom how ki-woo's father didn't notice his son laying down blooded while entering the basement after commiting atrocity in the backyard? How ki-woo figured out that his father "might" be hiding in the basement all along.