I’ve had issue under the kitchen slide with the 12v wiring.
The 12v wiring on our ‘17 Bighorn exits the frame and is in the loom attached to the flat piece of carrying poly.
The 110v is the black extension cord like cable that comes from the rectangular junction box on the frame.
The lights should be 12v and any receptacles are obviously 110v. Two separate power sources
Do you have a volt meter or multi tool? I’d test wires to determine which wire is carrying 12v & 110v. It would be difficult to say what color wire does what IMO.
In our kitchen slide, I too have a junction box but it powers the 110v receptacles. The 12v wiring for the lights enters the bottom of the slide and continues up through the end wall cavity of the slide out. No junction box
Hope this helps. Others will likely chime in
Good luck