Sorry for delayed response, was dealing with college finals. Anyway, it probably was desync, and I have seen it before, though only occasionally. The server I had was just a regular server my friends connected to with Hamachi.
Also tested with fill command and got the same result. The command should have placed six droppers facing north. The first two had stone north of them and faced south instead. The next three had air and faced north. The last one had glass and faced north.
Sorry for delayed response, was dealing with college finals. Anyway, it probably was desync, and I have seen it before, though only occasionally. The server I had was just a regular server my friends connected to with Hamachi.