All speakers but one are out but not blown and not sure how to gain connection

What is your question?

All but the backseat driver side speaker have gone out but not blown out. Each speaker went out at different times and rarely get a quick second back on. I’ve bought a new headunit hoping that would fix it but it didn’t. Want to see if there’s anything left to try before I have to rip the car open to check interior wires for the problem.

What makes this problem better or worse?

The more time I don’t solve the more speakers I’ve lost.

How long has your 2011 Volkswagen Jetta had this problem?

Almost a month