I have an idea of why this would be happening to some people and not others. I am going to do some research and try to get it fixed soon.

The blank tile issue is probably either an issue with your internet speed or Amazon's service. I host the map tiles on Amazon's servers (separate from the rest of the site). If either Amazon is not fast enough or your internet speed is having issues, you may have blank spaces. I am not personally having any issues with the blank spots.

I have never heard of the other issue. I will try it out. Are you adding route points using the "Default" mode or the routing mode? (Default uses the pop ups on the map; routing mode adds the points when you click on them.)