Power Assist Brake Vacuum Hoses, Lines/piping, And Fittings problems of the 2006 Volvo S60

I own a 2006 Volvo S60 r and I am filing a complaint for the loss of braking power when going uphill slowly or moderately fast. The condition will occur in any type of weather. Tires or brakes such as rotors and pads have no roll in the problem as reported by other owners and myself. My car has had this problem when it was brand new, with only a few thousand miles. The only way to get proper brake pressure back is to reapply the brakes again. I haven't been to the Volvo dealership about the problem because there is no reported fix for this issue.