PCF8563 RTC false reading
The chip expects a square wave clock signal, not a sine wave. Even worse, a long cable from the function generator to the chip can introduce ringing and noise.

Change your function generator to a square wave. Add a load resistor (50 ohms is common for function generators) directly at the chip input. Verify with an oscilloscope that the signal voltage does not go below ground or above the supply voltage of the RTC.