There may be a problem in the EarthSculptor program itself. I had problems with the program until I updated the drivers for the video card. But my problem is different from yours, so this probably won't be the solution.
The author of this video is CR!STALLL. He is in our SeriousSite discord. Most likely he will be able to help you. Besides, there are other people there who may know about your problem. Ask a question in the development channel.