Astral (Hurlcon) RolaChem RP9 pH only fault

[trashnetter]

Hi all
Im having trouble with my Astral RolaChem RP9 PH only system.
When the system starts up, all seems fine but after a while the display starts to show random characters as it scrolls through the normal information screens such as $#& etc sometimes replacing the normal letters in the information and some times just out in the edges of the screen.
The sensor does need to be replaced as the area of the sensor that is within the mixing cell has a crack in the plastic alongside where the metal pin for part of the sensor as well as it giving me a needs calibration warning when you can make it out in the garbled text. Im hoping someone out there has had a similar problem. Im also hoping that the sensor may be the issue as to replace the system will be quite costly. I need the system as I work away for weeks at a time.
Is there a generic sensor that is cheaper than Astral's?
I am an electrician and have opened up the controller and its in excellent condition, no pests or water ingress.
The system is also connected to a Connect 8 but I have isolated that from the RP9 and the Viron V7T chlorinator so the only real connections at the moment to the RP9 is the power from the VX7T and the PH probe. Everything else seems to be working correctly in the system.
Any advice from those who have had similar issues would be great.
Thanks in advance

couple of example pics below

https://ibb.co/album/jWDrva