Questions about Analog Inputs KC868-A16

[Decilitr]

I bought two boards from Kincony - KC868-A6 and KC868-A16.
The analog inputs of these boards were configured identically in exact accordance with the video https://www.kincony.com/forum/showthread.php?tid=3499
However, they show the voltage value completely differently.
The KC868-A6 board shows absolutely correct input voltage values for all four inputs in the range from 0.1V to 5.0V.
The analog inputs of the KC868-A16 board show incorrect and overstated voltage values.
To understand the situation, here is a table of values:

Real input voltage      Voltage displayed by the board KC868-A16
1.2V -------------------- 1.84V
1.5V -------------------- 2.21V
2.0V -------------------- 2.94V
2.5V -------------------- 3.65V
3.0V -------------------- 4.37V
3.5V -------------------- 5.04V
4.0V -------------------- 5.04V
4.5V -------------------- 5.04V

As you can see, the board displays very high values of the input voltage.
However, starting from a value of about 3.2V, the displayed voltage is 5.04V and does not change further.
This situation occurs for all four inputs of the board KC868-A16.
What's the problem here?