One SICK ultrasonic flare flow meter is installed in our HP flare line and we noticed that flare flow meter reading is little bit erratic while the flow rate is high. Recently we have some upset in our propane skid so we flare it the total gas and during that time we noticed the inlet ultrasonic meter reading is less than the flare ultrasonic flare meter. The flare flow meter is corrected with pressure and temperature. Based on the DCS trend the deviation is increased with flow rate. I expect some valuable suggestion to fix this issue and why this is happening.