Yes, exactly the same problem with my 2 year old Dewalt 18v . It was okay when new, but now after a lot of serious concrete drilling and large drill work, the snap action of the brake upon trigger release always causes the chuck to loosen. If the speed is slowly reduced the braking is less or not at all and the chuck is okay, I doubt that the chucks on these lower end machines are of good quality anyway, and since it has resisted all attempts at removal to fit a new one I'll live with it until I need a new one.
Trevor