I have the same problem. The microcode of the Core2 seems to be very bugy

I am facing a realy strange problem. If i leave the marked line (see NOT WORKING IF THIS LINE IS REMOVED) away then the display remains black. With this line its working. Since this line should not have a relevant effect on the general programm i wonder if this is a bug in the library or if i am doing something wrong. Any hint?

#include <M5Core2.h>

#define TFTW 320 // screen width
#define TFTH 240 // screen height
#define TFTW2 160 // half screen width
#define TFTH2 120 // half screen height

void setup()
{
M5.begin();
Serial.begin(115200);
showThermostat();
}

void showThermostat()
{
M5.Lcd.fillScreen(TFT_BLACK);
M5.Lcd.setTextColor(TFT_GREEN);
String text = "-28 ";
M5.Lcd.setTextSize(8);

int xpos = TFTW2-M5.Lcd.textWidth(text)/2;
int ypos = TFTH2-M5.Lcd.fontHeight()/2;
M5.Lcd.drawString(text, xpos, ypos, 1);
M5.Lcd.drawCircle(210, ypos, 5, TFT_GREEN);
M5.Lcd.drawCircle(210, ypos, 4, TFT_GREEN);
M5.Lcd.drawCircle(210, ypos, 3, TFT_GREEN); // NOT WORKING IF THIS LINE IS REMOVED
}

void loop()
{
}