From the “Joists? We don’t need no stinkin’ joists!” Department, here an unwise contractor decided to figuratively cut corners, and literally cut a floor joist right out. Folks, these joists are there for a reason. Namely, to hold your floor up and keep it from bouncing! The contractor also left a chunk of wood being held up by the electric wiring. My inspector wouldn’t like that! We can fix this, but you shouldn’t let a contractor get away with it to begin with.
If your system looks like this, get help! And one lesson for today is make sure you choose a quality contractor.