These occur all over the place and have been spoken about many times. I suspect it is more likely a lag / loading issue rather than an missing texture bug. If you go back to it or relog they normally fix themselves.
Hey, @Tunapiano. As @Lox said, sometimes bits of the world will go missing due to the environment not loading properly. Relogging can help the game find these missing elements. If you're seeing an excessive amount of these boxes and they are interrupting your ability to play, you may want to try lowering your graphics settings.