Speakers in the back not working anymore. Config or Hardware error?

I bought a Seat leon like 1 year ago with 6 speakers.
4 Of them being in the cockpit and 2 of them being in the backseat doors.

When I switched into the sound configuration I had the option to change the focus between left and right and back to front.

Today I just noticed I wasn’t able anymore to move the focus between back and front, after a bit of investigation I also realized that the speakers in the back doors aren’t giving any output anymore.

Is this something I can fix by configuring it myself or is it a known error I have to go to a service station to get it fixed?