All left speakers don't work on AM or FM but work fine on CD, tape and Nav.

I just installed one of my spare radio and all is fine so obviously the issue is with the radio.
Any ideas?

Update:

Well it turned out not to be the radio since the same issue came back after 1 hour of driving.
I unpluged all the connector the the amp, Nav module and cd in the trunk and so far it seems to have done the job.