Cannot connect WiFi in AP mode when using a hardware timer

[Modulex]

When the client(smartphone) tries to connect after starting the hardware timer on the server (ESP32), it does not connect to the server.
The timer cycle cannot be changed.
How can I solve this isue?

Thank you very much in advance,

#include <WiFi.h>
#include <WiFiAP.h>
#include "esp_system.h"

WiFiServer server(80);

const char *ssid = "AP";
const char *password = "";
const int localPort = 10000;
const IPAddress ip(192,168,13,2);
const IPAddress subnet(255,255,255,0);
hw_timer_t * timer = NULL;
int Counter = 0;

void IRAM_ATTR onTimer();

void setup() {
Serial.begin(115200);
pinMode(2, OUTPUT);
WiFi.softAP(ssid, password);
WiFi.softAPConfig(ip, ip, subnet);
IPAddress myIP = WiFi.softAPIP();
server.begin();

timer = timerBegin(2, 250, true);
timerAttachInterrupt(timer, &onTimer, true);
timerAlarmWrite(timer, 30, true);
timerAlarmEnable(timer);
}
void IRAM_ATTR onTimer(){
//timer cycle: 940us(was mesured by osilloscope)
static boolean tim= false;

digitalWrite(2,tim);
tim = !tim;
Counter++;
}

void loop() {
Serial.println(Counter);
delay(100);
}