What exactly happened within that 2 blocks? Same problem? New problem? One thing you have to understand with motorizing a bicycle is that there are going to be a bunch of little problems that pop up that need some solving. The vibrations alone will loosen hardware and the quality of some of the parts is just awful because of how cheap it is. Eventually you will work out the kinks, it just takes some patience and effort. This is one of the reasons I have been taking it nice and slow with my newest build with my Phantom 85. New bike, new motor with... not the best reputation for reliability if we are honest, and lots of new cheap parts. I've gone over my bike the aach time after the three times I have taken it out, and each time I found something that needed to be tightened again, loctite applied, or a jam nut added (also with loctite).