Uno to ESP32 - HardwareSerial repeats value on ESP32's side even though Uno is disconnected

Question

I have an Arduino UNO connected to ESP32 through voltage divider with TX0 from Uno to RX2 to ESP32. My goal is to send data from my Uno to my ESP32 through HardwareSerial. Here's my code for the Uno:

void setup() {
Serial.begin(9600);
}

void loop() {
int t = 100;
String myString = String(t);
Serial.println(t);
delay(5000);
}

Here I assign an int to 100 and then cast it to String so I can send it on my ESP32's side. My code for ESP32 is:

#define RXD2 16
#define TXD2 -1

HardwareSerial Serial2(1); // Use UART channel 1

void setup() {
Serial.begin(9600);
Serial2.begin(9600, SERIAL_8N1, RXD2, TXD2);
}

void loop() {
if(Serial2.available() >= 1){
Serial.print("Data received:");
Serial.print(Serial2.readString());
}
}

The serial monitor on ESP's side is printing only "100" on every 5 seconds but if I disconnect the Uno from my Port, the ESP's monitor keeps printing "100" even tho it shouldn't. However, IF I type Serial.println("100"); then I get "Data received: 100" on ESP's side and if I unplug the Uno, the ESP's monitor doesn't print anything or with other words it works properly. Is there a way I can fix this?