STCS1PUR went flashing after connected to power. Need a solution.

[TSu.1]

I am using the same schematics as the datasheet's typical application schematics sugguests. The EN and PWM pin were tied together with Vin. When I connect it to 12V power, It went steady for a couple of seconds then it starts to flash, it turns off and on periodically. so I removed the drain capacitor and connect it across the LED string to Vin (as another question post discussed), it did not solve the issue. What is causing this flash?