Analog Module Irregular input value (SM 1231 AI4)

I have my 6ES7 231-4HD32-0XB0 (SM 1231 AI4) Analog Input Module for my project. It receives 0 to 5 VDC as voltage input and I have a problem with my analog inputs

Here is the graph of my analog inputs (IW64 & IW66) built into the CPU. For months of using the PLC, all of the analog inputs in analog modules are working like this. Upon supply of 5VDC, PLC will have 13000 to 14000 decimal values. See graph 1

After modification in the program, we encounter irregularities in analog inputs on analog modules. Upon supply of 0 to 1 VDC, the decimal value in PLC will spike up to 65000 decimals. Then as you can see on graph, upon supply of 2.3 VDC, the decimal value in PLC will drop to 0 decimal. See graph 2

I tried to check the settings for the analog module but I don’t see any relevant parameter that can affect the analog inputs. I also tried resetting the PLC to factory default, but still didn’t work. I also isolate the electrical wiring of the PLC but still didn’t work. I check the analog input from the sensor but it gives the voltage correctly upon testing on the multimeter. We also tried other sensors but the same result.
I would like to know the possible reason for the analog input irregularities. Is it in the parameters? Wiring? I hope you can help me with this. Thank you in advance.

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Split from S7-1200 extended module malfunctioning.

Closed cause question posted twice.

The second thread with the subject Analog Module Irregular input value is published within the conference SIMATIC S7-1200