I want to stop having problems :(, I'm just missing this and I can't solve it

I don't know why input A on my Traktor 6 board reads in mono, it's not a cable problem since I tried changing the cables and the problem is input A, I cleaned the arm connection and it's not that either, use hysopropyl for If it helps to clarify that the problem is not dirt, I attach photos. If anyone knows or advises me what it could be or how to solve it, I would be very grateful. I really want to click.

Here is the photo of the problem :/

The B reads it well but the A reads it in mono, I don't know if the RCA connector is broken or what's wrong :( When I use it to listen to vinyl it reads stereo but obviously the signal does not arrive since it must be phono