Yamaha AG03 - no longer has a working guitar channel

[bass_dinger]

My Yamaha AG03 no longer has a working bass  guitar input ( channel 1). There is no sound via the mixer, although the peak level lights show that there is a signal going in.

 

However, when I switch to channel 2/3 (stereo keyboard), the AG03 produces sound. 

 

I have tried swapping cables  - channel 1 does not work, but plugging the bass into channel 2 gives me sound. 

 

This happened once before  - no sound from channel 1, but it started working again,  by itself.

 

Any ideas? Maybe a factory reset? Buy another interface?