Aduc832 crystal

Hello:

Aduc832 crystal  uses 32.768KHz watch crystal .The problem is, the frequency locking of aduc832 is inconsistent. When entering the download mode, the default BPS is 9600.  the serial port waveform from oscilloscope, each bit width is sometimes 82us, 94US and 110us.

I use crystal oscillator capacitor of 12.5pF, and 832 is internally integrated with 18pF, so I have the above problems after several capacitance capacitance tests on the externally connected capacitor.

Please help me with the problem, thank you