I guess the problem won't occur with resistor load and is most likely caused by incandescent lamp increased inrush current triggering TNY278 current limit.
I'm not sure if the device is well suited for this kind of load. If you don't expect permanent overload, you might try increasing the current limit by using a 10 µF C10 capacitor as described in datasheet. You can also try if you achieve stable operation when the output voltage is slowly increased to the final value, in this case a RC combination parallel to R12 could provide a voltage ramp.