Pioneer DJM-800 Crossfader damage?

Hey Guys..

I bought a used DJM-800 and tested it a little. Then I realized, that if I put Channel 1 to the left-side, another channel to the right side and put the crossfader right to the left, I can hear the Song On Channel A and B (B is a little more quiet). But if I push the crossfader to the right side, I only can hear Channel B.  Is my Crossfader damaged or are there any settings I missed?

Thanks :=)