Software serial gives unreliable results

Projects Programming
3

Thanks for your reply.
I changed the code in the void loop to:

void loop()
{
  while(gsm.available())
  {
    incoming_char = gsm.read();
    Serial.print(incoming_char);
  }

    gsm.println("AT");
    delay(700);
}

Only with the 700 ms (and longer) delay I get no errors. So it seems to be a buffer overrun.
I will have a look at my original code next week and see if I can solve the problems there too.
Thanks again.