Speech recognition and LCD slowdown on Maixduino

When I try to use speech recognition and the LCD I get a slowdown on the screen. You can see it in the video below (23 secs in)

Full code if you want to see it: https://github.com/robotzero1/maixduino-multiauth

Also short test code showing the problem:

#include <Sipeed_ST7789.h>
#include "Maix_Speech_Recognition.h"
#include "voice_model.h"

SpeechRecognizer rec;
SPIClass spi_(SPI0); 
Sipeed_ST7789 lcd(320, 240, spi_);

void auth_voice()
{
  rec.begin();
  rec.addVoiceModel(0, 0, red, fram_num_red);
  int res;
  res = rec.recognize();
  Serial.printf("res : %d ", res);
}

void setup() {
  Serial.begin(115200);
  lcd.begin(15000000, COLOR_BLACK);
  lcd.setTextSize(2);
  lcd.setCursor(10, 40);
  lcd.println("Before voice...");
  auth_voice();
  lcd.setCursor(10, 80);
  lcd.println("After voice...");
}

void loop() {
}