Conventional ammunition (IE nonexplosive machine gun rounds) can't be activated by electricity. To my knowledge they require impact to the back of the shell cases to ignite a very confined spark that ignites the gunpowder that shoots the bullet forward. At the very most, the robot would shoot up a few of its internal mechanisms, though I doubt the bullet feed is right by anything important.

Thing is, we don't need to get this technical. The same knowledge that aids our characters against the Grimm will work on this robot: no armor is perfect, and it will have weaknesses. Whether they be small uncovered points, loose bits like cables or wires, or armor that can be pried off, we can get around its metal shell and at the circuitry beneath. To quote Cheetor: "If you're bashing bots, hack at the hinges."

Plus, we don't even need to get it right the first time. With the robots turrets disabled and its chest-guns inoperable, it'll have to resort to melee. And despite its size and crushing strength, I'd say four super-powered teenagers in a whimsical world could beat it to death without any huge complications.