In the last lock, PI31 at 10.428 kHz rang up as shown in the first attachment. Although it was damped by SUS_PI guardian, PI31 RMSMON reached close to 2000. The frequency of this PI is 10427.67 Hz as shown in the second attachment. This is within the input bandpass filter (425-431 Hz after downconversion by 10kHz). I increased damping gain for PI31 from 1000 to 10000 in SUS_PI guardian.

EDIT: This gain increase was too much. I reverted the damping gain to 1000 in SUS_PI guardian.