1. Anytime you give someone freedom to create (anything), you will end up with a penis drawing. Just scrolling through quickly I see that Frame #13122 delivers on this law of the universe. After watching the movie preview, I only watched the first 45-50 seconds and counted about 4-5 drawings of the bodypart and 6-8 additional frames that just contain the word "penis". I wouldn't be surprised if 2-4% of the total frames submitted contain this specific content.
2. It says that all frames have been drawn, but in fact they are far from complete. Many people have submitted blank frames or frames with one line scribble. There really should be a minimum "ink" or "coverage" amount before determining that a frame has been given a proper amount of effort in the drawing.
3. People have wildly different artistic capabilities. Which sounds like part of the fun, but in practice many of these frames are so bad, that watching them back to back just looks like a static mess.
4. Not a problem, but there are also some AMAZING submissions in here that are awesome to see. I wish those people could be allowed to submit additional frames. Maybe enough "upvotes" on their existing frames and they get to create another frame.
5. We need to crowdsource a review process. It would be good to allow people to either A) draw a frame, which is a smaller portion of the population or B) review an existing frame for content and quality. This allows everyone to contribute to the movie in a way that they are capable. Reviewers could be shown a frame with a few buttons such as: blank, low effort drawing, inaccurate drawing, inappropriate drawing (see #1). If a frame gets a high ratio of similar negative reviews then we know to put it back into the rotation to be redrawn.
5. Just because all frames have been drawn, there should be the option to resubmit an alternative for low-effort or blank frames. These are easy to find, so I should be able to submit a second drawing that gets queued behind the original in case the original gets rejected through the review system (which a blank frame easily would).
Overall the concept is really cool. These tips above would solve most of the core problems and make it a better experience for everyone.