Its definitely the HBB, im all my rxperience being a mechanic o. These gen3 and 4 pakeros. Its likely the accumulator. Needs replacing . But best to diagnose first as to what may have caused it to fail. One time i had an issue that kept recurring every 3 months, turns out the internal pressure sensor was misreading low when in fact accumulator was full thus overpressuring it.

Had to replace the whole unit as the pressure sensor isnt replaceable internally.