Adjusting the time on DS3231 with encoder, TimeLib.h and DS1307RTC.h

I think that your rtc adjust time function should look like this.

void adjustTimeEnc(int deltaTime){ // deltaTime is an integer from -4(negative 4) to 4(positive 4) (excl. 0) depending on the acceleration of the encoder
  
 unsigned long newTime = RTC.get() + deltaTime*60000L;
 RTC.set(newTime); 

}