Noisy ram, failing pump?

[masonc]

I have a Raymarine ST6000 autohelm with a Octopus Hydraulic ram system. The pump is a 1012.
When active, the pump makes a groaning sound when pumping. I thought it was something obstructing the ram but it is clear.
After a while, I get an MOT fail error, and the ST6000 gives up.
I checked for low hydraulic fluid, topped up the cylinder. I bled the cylinder.
I'm thinking it could be bad brushes on the pump. Anyone had a similar problem with this unit and solved it, other than complete replacement?