2010 G37 convertible with 59000 miles has been retracting both front seatbelt when the brakes pedal is applied even moderately. Vehicle was taken to a dealer where a brake booster "leak" was found and the brake booster replaced. Front brake pads were replaced and rotors resurfaced. The original problem was solved at this point. One week later, the original problem is back. We are waiting for an appointment to get the car back into the dealership repair facility. Anyone have a clue what is going on. Have had this vehicle for seven years. First real "problem".

Got back to the dealers shop and they now want to replace LH and RH pretensioners. Are the pretensioners not working when they retract the front seat belts when the brake is applied? Is there someone with a better solution?

They'll be under warranty, so if the dealer says they need replacing, let 'em do it.

They should not retract upon brake application, only upon deceleration (should have an inertia switch).

The seatbelts retract only when the vehicle is being slowed down with the brake. I was quoted about $700 just for the replacement pretensioners. Are they lifetime warranty items?

Anything seatbelt related should be covered for the life of the car, I would think.

If they're working correctly, they don't need replacing.

None of the regulations or statutes administered by NHTSA require manufacturers to provide a lifetime warranty for seat belts. However, NHTSA has the authority to require manufacturers to replace seat belts under certain circumstances. If a vehicle or item of equipment is not more than ten years old and is determined to have a safety-related defect or fails to meet an applicable Federal motor vehicle safety standard, NHTSA can compel the manufacturer to remedy the defect or noncompliance without charge to the vehicle owner.

According to Nissan’s 2019 Warranty Information Booklet...

Overview Of Nissan’s New Car Warranty
10-Year/Unlimited Mile Seat Belt Warranty: All defective parts of your seat belt system are covered.

The dealership replaced both pretensioners and the original problem is gone. There was the 10 year warranty issue but they replaced them at no additional charges to me. I was out of the the cost of the alleged Leaking brake booster and labor. Last visit to this dealership was Sept 2020.