How can we set BF561 to be Full-On Operating Mode

Hi, We are using ADSP-BF561SBBCZ-5A for data processing.

We want BF561 to work under Full-On Operating Mode, and set PLL_CTL to be “0X2200”, but sometimes it failed (the processing speed is lower than expected). When it failed, we found that PLL_CTL=0x2200, PLL_DIV=0x0004, VR_CTL=0x00DB, PLL_S         TAT=0x00A0, PLL_LOCKCNT=0Xdbb8.

Actually if we run it 100 times, about 5 to 10 times it will failed. Can anyone tell me the possible reasons? Thanks