I had the exact same problem..troubleshooted everything under the sun. In fact, neptunes forum is filled with complaints about this exact issue. I still think there might be something weird with one of the recent firmwares, but they won't acknowledge it. As for my troubleshooting steps, I completely isolated the cable, recalibrated my temp prob (which happened to be off, you should check that if you have a good hand held temp gauge), cleaned and recalibrated the salinity probe, checked for stray voltage...you name it, I did it. Yes, you should recalibrate your probe, second, make sure its in a high flow area. I found mine to be the most consistent when I dropped it in my overflow tube. Sounds stupid I know, but it works, and it varies A LOT Less than it ever has. Neptune told me that unless you crack the probe inside, or never clean it, the probe should last a long time.
