Rotary potentiometer nor reading linear
The potentiometer is a B10K rotary potentiometer and its power and ground come from the PCB.

And you have it loaded by a 1.7k + 3.3k = 5 kΩ potential divider.



simulate this circuit &ndash; Schematic created using CircuitLab
Figure 1. The equivalent circuit.

Figure 2. The output voltage as a function of potentiometer rotation.
Your potential divider is overloading the potentiometer. As you get closer to the top of the pot it begins to be able to control the load a bit better.
You should increase the potential divider resistance to be at least ten times the pot resistance.