You may have accidentially touched a region of your plate you had already streaked without realizing it and then streaked your 4th quadrant. That has happened to me a few times. Or perhaps the loop did not get adequately flamed before your last streak. It's sort of difficult to say, but just be careful and make sure you consciously go through all the steps the next time you do it until you get comfortable. Then it will become unbelievably easy and almost thoughtless. Hope you have better luck next time!