Front speakers cuts/dies when turning volume up

[TP_]

Hi!

If someone has any theories regarding this I´d be very happy, I´m almost planning on selling the darned D3 because of this.

When I start the car, 9 out of 10 times the stereo works fine and 1 out of 10, the front speakers are dead.

When I start the car and the front speakers work, they stop working after turning up the volume. The typical scenario;
"Ohh, finally a good song, let´s turn the volume up".
And then, snap, only rear speakers (including door speakers) work, such a disappointment.

A few times I´ve gotten them to work again by twisting the whole cable-thingy that goes into the amp at the left side of the trunk, but most times nothing happens.
Sometimes a restart of the car works.
MMI reset usually doesn´t do a thing.
Sometimes the front speakers starts working again during hard cornering, like there´d be some unwanted play somewhere.

This is neither Bose or B&O, it´s the standard stereo with a subwoofer.

Oh, and VCDS doesn´t show anything.

Thanks/
Mattias