I have a question. How did you create spit surface of tooth (I marked it on screenshot)? Could you show me your model tree or explain how you split this surface?? I have your file from youtube, but I don't have education version and I can't open it.
I Created gear and pinion but I have a colission between parts. I noticed, you use in assemby other parts with split and your gear connection is OK.
Below is my result of your tutorial. There are any split on tooth's surface