C1391 Brake Booster Pump and Actuator - Accumulator Leak Malfunction

[Cumfigali]

Hi, have the C1391 code fault, and the brake booster pump cutting in about every 8 seconds. Fluid level is fine and no apparent leaks. So it looks like I have either a faulty booster pump or the actuator is gone. I can reset the code but it comes back up after a bit of use. Braking system is working, but it needs seeing to.

Has anyone had this issue? And any checks to carry out to establish which item is at fault. Or other things to check? This is going to be expensive no doubt so I want to get it right and not just random part changing.

Also part numbers for both item for RX450h 2010. The only parts that pop up online are used and I'm not going down that route. Thanks