Tone control circuit issues and dead subwoofer output

When I'm playing audio through the receiver it will work fine for an 30 minutes and sometimes longer, the the right front and center channel will start cutting in and out. When I put the receiver in Direct mode the right doesn't cut out but I only get stereo output.

The subwoofer rca out has never worked since I got the things.

I have opened the receiver and I saw not burnt or popped components.

Can someone help please.