BMW UK Tech finds the ongoing rattle

[Fullfast]

All

Need some advice......was asked to take my E70 in today so as a Senior BMW Technician could pinpoint the ongoing noise that is coming from the rear of the car....

After 20 miles with him laying in the boot and moving various pieces of trim he has isolated it to the area around the rear C pillar of the vehicle and has said that it is more than likely a spot weld that has come apart........

I had already notified the dealership of my intent to reject the vehicle if this was not resolved this time, this was before the broken weld.....

What I am looking for is advice on whether I should reject the vehicle now or let them attempt to resolve the issue......

Would you be concerned if a weld had come undone ???

Thanks in advance