Big swings in the conductivity probe

[AlexTm]

Hello, so I left the probe in a bigger cup for more time.
Here is the graph.
long.JPG

After first try I moved the probe back to tank, then back to a larger cup and left it there, it is still there and I am not touching the cup in any way.

Later Edit: even longer:
longer.JPG

What can I do about this? The behavior is present since I bought the P4.
whole.JPG