MP6538 driver tripping issue after 70% duty cycle

Hi
I am using MP6538 BLDC driver.
My motor runs alright till duty cycle is about 70% but after that suddenly drive trips.
Below 70%, driver works fine and even current limiting also appears to be working ok.
I have tried various values for DT and OCP filter, MOSFETs are fired within 2 microseconds.
Even if I tied the OCREF pin to Vref via 100k as suggested in the application note, drive trips.
I will greatly appreciate your valuable inputs.
regards
Shirish