There is no dry side, both halves are identical so, yes, both are water proof.
The nano Streams are a new product, as with most new products there are unforeseen problems that occur in early production. We have worked hard to solve these problems and the next batch should be free of these issues. In early pumps the shafts came free of the hole they are pressed into in some cases as the fit was too loose. There is a "thrust washer" under the drive unit, we call it a disk. Your prop was miscut, for 60Hz the 50Hz prop is cut on a lathe, it likely was that way out of the box and you need a new one, I have seen a few of the first pumps with this problem.