I buy redox probe for my profilux 4 and it don't work.
I have calibrated it four times and it shows strange readings.
First and second time it rises slowly, in 2-3 days readings goes over 500. Then I search answers here on forum and some discussion you give advice that try ph probe to port and see if it starts to rise, yes it did, slowly as redox, in 2-3 days it shows 0.10 over real value of ph. I change redox probe back to port and calibrate it, after calibration it was first time that it shows value around 220 from calibration fluid, earlier times it showed 160-170. After this calibration it give good readings about 6-7 days, after that it start to drop towards zero and then it go under zero and show reading -500 week after.
I calibrate it again and after 3 days it show again readings below zero.

I do calibrations as should, use null plug, your calibration fluid 220ms.

What I must do that redox probe starts to work or is it broken?