Yep, I get this nearly every night riding at to work. It's not the weight, sensors pick up the metal in the scoot, or some such.
I found that if I roll all the way to the front of the sensor area (sometimes onto the stop bar) I can get it to trigger the light....if not, I hang a right, then a U-turn, then a right to go straight on through the light..
My riding instructor said if you get stopped by police you can site the malfunctioning light law to justify going thru a red light after a stop on 2 wheels.