ESP32 keeps rebooting when I try to save the current timr in SPIFFS

Question

I am trying to save the current time & date into SPIFFS from a web page hosted on ESP32 but for some reason, the ESP32 reboots when the button <button type="button" onclick="sendTime()">Record Time&Date</button> is pressed.

JavaScript:

    <script>
function sendTime() {
  // Get the current time and date
  const now = new Date();
  const dateStr = now.toLocaleDateString();
  const timeStr = now.toLocaleTimeString();

  // Create the request body
  const body = {
    date: dateStr,
    time: timeStr
  };

  // Send the HTTP POST request to the server
  fetch('/save-time', {
    method: 'POST',
    headers: {
      'Content-Type': 'application/json'
    },
    body: JSON.stringify(body)
  })
  .then(response => {
    if (!response.ok) {
      throw new Error('Error saving time to server');
    }
  })
  .catch(error => {
    console.error(error);
  });
}
</script>

And the ESP32 server-side code:

Libraries used: WiFi.h, FS.h, SPIFFS.h, Arduino.h, ArduinoJson.h and ESPAsyncWebServer.h

setup() code snippet:

// Initialize SPIFFS
  if (!SPIFFS.begin(true)) {
    Serial.println("Failed to mount file system");
    return;
  }
  Serial.println("SPIFFS mounted");

  // Set up routes
  server.on("/save-time", HTTP_POST, [](AsyncWebServerRequest *request){
    // Get the request body as a string
    String body = request->getParam("plain")->value();

    // Parse the request body as JSON
    DynamicJsonDocument doc(1024);
    deserializeJson(doc, body);

    // Get the date and time from the request body
    String dateStr = doc["date"].as<String>();
    String timeStr = doc["time"].as<String>();

    // Create the file name using the date
    String fileName = "/watering-" + dateStr + ".txt";

    // Open the file for writing
    File file = SPIFFS.open(fileName, FILE_APPEND);
    if (!file) {
      Serial.println("Failed to open file for writing");
      request->send(500, "text/plain", "Failed to open file for writing");
      return;
    }

    // Write the time to the file
    file.print(timeStr);
    file.print("\n");

    // Close the file
    file.close();

    // Send a success response
    request->send(200, "text/plain", "Time saved successfully");
  });
  // Route for retrieving watering times
server.on("/watering-times", HTTP_GET, [](AsyncWebServerRequest *request){
  String response = "";

  // Get a list of all the files in the / directory
  File root = SPIFFS.open("/");
  File file = root.openNextFile();
  while(file){
    // Check if the file name starts with "watering-"
    String fileName = file.name();
    if (fileName.startsWith("/watering-")) {
      // Read the file contents and add them to the response string
      response += fileName.substring(10, 20) + " " + file.readString() + "<br>";
    }
    file = root.openNextFile();
  }

  // Send the response with the list of watering times
  request->send(200, "text/html", response);
});

  // Start the server
  server.begin();
}

as soon as the button is pressed ESP32 reboots and prints this in Serial:

Guru Meditation Error: Core  1 panic'ed (LoadProhibited). Exception was unhandled.

Core  1 register dump:
PC      : 0x400dec30  PS      : 0x00060e30  A0      : 0x800dec6e  A1      : 0x3ffd2280  
A2      : 0x3ffd230c  A3      : 0x00000010  A4      : 0x00000005  A5      : 0x0000ff00  
A6      : 0x00ff0000  A7      : 0xff000000  A8      : 0x800de95c  A9      : 0x3ffd2260  
A10     : 0x00000010  A11     : 0x00000000  A12     : 0x00000006  A13     : 0x3ffce334  
A14     : 0x00ff0000  A15     : 0x00000002  SAR     : 0x0000001b  EXCCAUSE: 0x0000001c  
EXCVADDR: 0x0000001f  LBEG    : 0x40089db9  LEND    : 0x40089dc9  LCOUNT  : 0xfffffffe  


Backtrace: 0x400dec2d:0x3ffd2280 0x400dec6b:0x3ffd22a0 0x400d45a2:0x3ffd22c0 0x400d48a5:0x3ffd2390 0x400dbbf9:0x3ffd23b0 0x400d9fbd:0x3ffd2400 0x400da02d:0x3ffd2450 0x400dcca5:0x3ffd2470 0x400dcd21:0x3ffd24a0 0x400dd32a:0x3ffd24c0




ELF file SHA256: 78ff020431f74c0c

Rebooting...