Flipping the direction of the IC’s from source to linestage, the vocals become unintelligible and music sounds odd.Put them back as the arrows indicate, vocals/music fine.Yes if you use rca interconnects with two wire (red/black) + shield, if they did it right thing, the shield is only connected to the black at one end.
Pay attention to those arrows!
This end is used to dump any RF collected by the shield to ground, at the least sensitive component in the chain, and should be the way the arrow points if there.
Cheers George