Kenwood KA-2500 Integrated Stereo Amplifier Vintage Audio

Description

I believe this Kenwood KA-2500 is working or mostly working as it should.  I hooked it up to an external audio source to the AUX channel and it plays music out of the A speakers and the B speakers when switched between the two.  However when I switch it to A + B speakers it didn't play, I'm not sure if it is something I'm doing wrong or it has an issue.  I didn't test any of the other input or tape options.  See pics and included video for demonstration
Kenwood ka-2500
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