Larry is right, if you want to fix this system talk to Raritan.
That toilet is a very old model and I would recommend up grading to a newer design rather than spending money on it.
The new Raritan Marine Elegance toilets are quiet and reliable.
Raritan Engineering | Marine Elegance
Is your treatment system an Electro Scan or the older Lectra San? If it is the older Lectra San, replace it. If it is the newer Electro Scan, fix it.