Jessica's pregnancy seems to progress and recede without any regard to chronological order.
When Paul and his mother are stranded in the desert, Paul has several days' growth of beard. When he is rescued on board the 'thopter and is strapping in, he is clean-shaven. When he arrives at the caves, the beard is back, and when he leaves and is aboard the 'thopter, he is clean-shaven again.
At the very beginning of Part 2, the title screen says "Maud'Dib" when it should read "Muad'Dib."
The human body consults of 70% water, so when the Watermaster says they have 33 liters of water, that would be far too little for a grown man, the quantity should have been closer to 55 liters.
The human body consists of 70% water, so when the Watermaster says they have 33 liters of water, that would be far too little for a grown man, the quantity should have been closer to 55 liters.
When Paul and Chani are in the desert together, and Chani is in front of their tent waiting for him, all the blue from her eyes is gone.
In the opening scene of the second part, where Baron Harkonnen is sobbing as the Fremen are chanting Muad'dib, you can clearly see Paul Atreides duck down and run out to the right as the camera passes behind the Baron's head.
When Paul and Jessica leave the crashed ornithopter, Jessica asks where they are going. Pointing their para-compass, Paul says that they are going south. However, the sun is clearly low and directly at their backs. That should indicate that they are heading either West or East, depending on time of day. Also, it is the sun in the sky, and not a moon, since it is the main source of shadows.
The miniseries makes extensive use of painted backdrops made of cloth. This is very visible in some scenes, especially in the desert. The confrontation between Jamis and Paul is a good example for this cost-saving measure.
In the second part, when Paul and Jessica are walking on the dune to reach safety, the background behind them is clearly fabric by the texture.