I went tonight and decided to ride FOF as it was quite cold. The ride op was dispatching trains a lot quicker than normal. They usually seem to be waiting for something because they will sometimes announce "green cones", meaning that whatever they were waiting for is ready. Our train was dispatched very soon after the last one. As we were launching, I noticed that we were moving remarkably slower than normal. The train was moving at about 40 mph near the end of the launch when all of a sudden the brakes slammed closed. We stopped in less than 1 second. For some reason, we were not launched fast enough. Eventually, maintenance came and manually released the brakes and pushed the train all the way back to the station while everyone was still in it. A few test runs later, the ride was operating normally, except they decided to only use the front 3 cars. Made for a fun and interesting night!