My Aqualisa shower is making a terrible noise, even when turned off! I had to switch it off at the isolation switch.

The power would not kick in when turned on full, only worked when half way and at a lower pressure.

It had a new pump 10 years ago and a new thermostat 3 months ago.

Is this fixable or does it need replacing. They are so expensive I would prefer someone tries to fix it first.