How to set maximal execution time of operation

I'm JSON deserializing output from ESP8266 in my Arduino UNO, but when it fails (for some reason every time after it deserializes successfully) the program lags for few seconds and I don't want that to happen (at least not for a long time)

#include "SevSeg.h"
#include <ArduinoJson.h>
SevSeg sevseg; 

StaticJsonDocument<500> response;

String data;

void setup(){
  Serial.begin(74880);
  Serial.setTimeout(10000);
  while (!Serial) {
     // wait for serial port to connect. Needed for native USB port only
  }
  byte numDigits = 4;
  byte digitPins[] = {2, 3, 4, 5};
  byte segmentPins[] = {6, 7, 8, 9, 10, 11, 12, 13};
  bool resistorsOnSegments = false; // 'false' means resistors are on digit pins
  byte hardwareConfig = COMMON_ANODE; // See README.md for options
  bool updateWithDelays = false; // Default 'false' is Recommended
  bool leadingZeros = false; // Use 'true' if you'd like to keep the leading zeros
  bool disableDecPoint = false; // Use 'true' if your decimal point doesn't exist or isn't connected. Then, you only need to specify 7 segmentPins[]

  sevseg.begin(hardwareConfig, numDigits, digitPins, segmentPins, resistorsOnSegments,
  updateWithDelays, leadingZeros, disableDecPoint);
  Serial.println("running");

}

void loop(){

       if (Serial.available()) {
            Serial.write(Serial.read());
            const auto deser_err = deserializeJson(response, Serial);
       
            if (!deser_err) {
                
                if(response["type"] == "num"){
                  sevseg.setNumber(response["data"],response["dot"]);
                }else{
                  sevseg.setChars(response["data"]);
                }
                String data = response["data"];
                Serial.println(data);

            }else{
              Serial.print(F("Failed to deserialize, reason: \""));
              Serial.print(deser_err.c_str());
              Serial.println('"');
            }
            
       
  
      }

  sevseg.refreshDisplay();


}

The response

running  //runs everytime I turn on the arduino
21:43:03.797 -> {null
21:43:03.797 -> :null
21:43:03.797 -> ,null
21:43:03.797 -> :null
21:43:03.797 -> ,null
21:43:03.797 -> :Failed to deserialize, reason: "InvalidInput" // for some reason I have to send request 2 times because for the first time it always fails
21:43:03.797 -> 
Uove //correct data received
21:43:04.772 -> // this timestamp isn't right it is like 5 seconds after correct data
Failed to deserialize, reason: "EmptyInput"

What can I do for this not to happen for the first time or in a shorter duration?

I'd be really thankful for any answer.