What year is the brake? Normally speaking hope brakes do tend to come with a manufacturers warranty depending of where you purchased it from i doubt hope could do a free service it could be anything could be the seals, pistons etc.. or ote. Send it to tartybikes im sure adam could re drain the system clean it and re-bleed it. But tartybikes charge i think about £10 for a disc brake bleed seals dont cost that much but overall depends until a proffessional looks at it.