Abnormal Behavior in K vs. Time Graph in Depletion Run

Hello,

I recently conducted a depletion run usinig customised GFR assembly, and I encountered an unexpected behavior in the k vs. time graph. Instead of observing a decrease in k as time progresses, the graph shows the opposite trend. Despite thorough debugging efforts, I have been unable to identify the source of this anomaly.

I have attached the ipynb file containing the relevant data and code for reference.

Could anyone provide insights or suggestions as to why this abnormal behavior might occur? Any assistance would be greatly appreciated.

Thank you in advance.
k vs t