Fix blinking LEDs with a motion sensor (when off)
This is common with sensors that are not listed for use with LED’s 
The sensor is drawing a tiny amount of power to power the electronics, this s just enough to cause a glow and sometimes flashing. You have 2 options use higher wattage lamps like you have tried to prove the sensor was working OR find an LED compatible sensor. I use motion sensors that work with LED’s you will find many of the led type need a neutral so they power the electronics with out drawing current through the lamps this is causing the flashing.