The LED uses an inductor to integrate rectified AC to DC current. When the PIR decides to switch off the load, there is a chance of a flyback high voltage impulse, If the PIR sensor has no immunity to this, then a fault may occur.
It would have to be a relay to cause the flyback pulse. These are commonly used in AC PIRs.
If the PIR used an SSR like a Sharp S202xx, let me know.
To correct this hypothetical cause, a TVS or RC snubber may fix the problem across the load.
R=350V/0.5A = 700 Ohms, C = 1 to 4.7 nF X-class film cap. is my estimate.