If a moving block's starting position is right next to a static block, some faces of both the moving block and the static block are not drawn. As far as I have seen, the missing faces are exactly those where the moving block and the static block "meet" (in their starting positions).
See bug 3602621 for an example level.
Hi. Thanks for reporting. This, however, is not really a bug.
Moving blocks are not meant to be placed in a way that they touch the static world.
It is possible that we are allowing it in future releases. However, it is a bit hard to provide a consistent Cubo-physic in this case