MSP430F5418A: MSP430F5418A resonator issue on XT2

Hello,

i have a problem with a 4MHz resonator (Type CSTCR4M00G53U-R0) at XT2. It remains always in the loop, because the XT2OFFG flag is set.

Alternatively i tested it with a 4MHz crystal with 12pF load capacitance and it works, but the resonator always failed.

Has anybody an idea what could be the reason?

My code:

void SwitchXT2(U8 OnOff) {
  if(OnOff == ON) {
    _DINT();
    P5SEL     |= 0x0C;                        // Port select XT2
    UCSCTL6   &= ~(XT2OFF+XT2BYPASS);         // Switch ON XT2 oscillator    
    UCSCTL6   |= XT2DRIVE_3;                  // Highest drive setting for XT2startup
    do  {                                     // wait till oscillator is stable
      UCSCTL7 &= ~XT2OFFG;                    // Clear XT2 fault flags
    }while(UCSCTL7 & XT2OFFG);                // Test XT2 fault flag
    UCSCTL6 = (UCSCTL6 & ~XT2DRIVE_3) | XT2DRIVE_0; //set requested Drive mode
    UCSCTL4 = (UCSCTL4 & ~SELS_7) | SELS__XT2CLK; // switch XT2 as SMCLK source
    _EINT();
  }
  else {
    UCSCTL6 |= XT2OFF;                        // Switch XT2 off
  }
}