On my 9-month old XC40 I too noticed that the rear section of the panoramic sunroof has a series of cracks running parallel to the frame and across the rear section. The cracks do not appear to penetrate the glass. They appear to be stress-fractures, with slight heave where the cracks meet. There is no sign of impact damage which would also be accompanied by radiating fractures.
Volvo inspection today concluded that the cracks were due to stone chip damage - which I strongly dispute. Any impact to cause this amount of damage to toughened glass would have been noticed and certainly heard!e the issue with
Next step is to escalate the issue with Volvo UK Executive Office. 01628 422400