Boombox only works on one speaker with 2/3 inputs

[optonox]

Hi,

I have this boom box.




It has three modes:
- Tape
- TV
- Radio

Tape works with left and right channels but the TV and RADIO modes only have audio coming out of one of the two channels (I have swapped the speakers just to be completely sure).
The speakers have a 1/4" mono type plug.

Does anybody know why this would only be working in 2/3 modes or how I could go about debugging this?

Thanks

[shakalnokturn]

Bad contacts in function selector switch?