I have the same problem. The "Cell Temp Sensor" reading has been steadily climbing over the last several days and the salt reading is steadily going down. After about a week, the diagnostic menu of the control panel says my pool is a ridiculously high 180-degrees (F). The actual pool temp is below 80-degrees (F), so it is obvious that something is wrong somewhere in the cell temp sensor circuit. I suspect that the low salt reading is a programming side-effect of the high temp reading.
I wondering if you solved your problem and what the issue was. I've had motherboard issues with my Hayward Goldline controller in the past, so I would like to know if this is likely to be a motherboard issue, a connector issue, or a Turbo Cell issue.
I'd also like to know if the cell temp sensor can be replaced without replacing the entire Turbo Cell.