Stuck in an interrupt?

Evening
I have set the interrupt time to 25ms and checked via a oscilloscope. the reading of the receiver pulse works well, and the interrupt works when a pulse is missing, but i still get stuck in the interrupt.

#define ledPin 13
#define RxThro 3
unsigned long Time1 = 0;
unsigned long Time2 = 0;
unsigned long pulse1 = 0;
volatile boolean failSafe = false;
int FST = 15000;
boolean toggle = false;
void setup()
{
  Serial.begin(115200);
  pinMode(13, OUTPUT);
  pinMode(ledPin, OUTPUT);// initialize timer1 
  pinMode(RxThro, INPUT);
  noInterrupts();           // disable all interrupts
  TCCR1A = 0;
  TCCR1B = 0;
  TCNT1 = FST;            // preload timer 65536-16MHz/256/2Hz
  //TCCR1B |= (1 << CS12);    // 
  TCCR1B |= (1 << CS11);
  //TCCR1B |= (1 << CS10); 
  TIMSK1 |= (1 << TOIE1);   // enable timer overflow interrupt
  interrupts();             // enable all interrupts
}
void doCalcs()
{
  if (failSafe == true)
  {
    pulse1 = 900;
  }
  else
  {
    TCNT1 = FST; //reset the failsafe timer
    pulse1 = Time2 - Time1;
  }
}

void getInputs()
{
  while ((digitalRead(RxThro) == LOW)||(failSafe == true))
  {
  }
  Time1 = micros();
  while ((digitalRead(RxThro) == HIGH)||(failSafe == true))
  {
  }
  Time2 = micros();
}

ISR(TIMER1_OVF_vect)        // interrupt service routine that wraps a user defined function supplied by attachInterrupt
{
  TCNT1 = FST;            // preload timer with Fail Safe Time
  failSafe = true;
  toggle = !toggle;
  digitalWrite(13, toggle);
}

void loop()
{
  failSafe == false;
  getInputs();
  doCalcs();
  Serial.println(pulse1);
}