Question: There are many important characters in my novel. That's why I use a third-person omniscient perspective. When I write a book, the events come to mind like movie scenes. That's why I have to enter the minds of different characters in one episode. I have to constantly change the camera within the same section. Is this a problem? If this is a problem how can I fix it?
It's not a problem necessarily. You just have to recognize that there are pros and cons with every narrative mode.
Omniscient narration has the advantage of being able to switch easily from character to character and place to place. The reader has the sense of being like "a fly on the wall," watching the events unfold.
The disadvantage of omniscient narration is that it often gives readers the sense of "looking at" characters rather than "being" one character in particular. It's a more objective, less intimate experience.
If you are going to narrate what's going on inside the minds of different characters, you have the added challenge of making sure the reader still feels like they are looking at the characters thoughts and feelings objectively rather than subjectively. The perspective has to remain consistent, even as you move from one character to another, so that the reader won't get confused.
If this is not done well, the reader can feel like they are looking at the events from the perspective of one character, but then get confused when presented with another character's thoughts or feelings. Suddenly, they don't know what perspective they are occupying.
For this reason, it is often safer to use third person limited narration, but with a number of point-of-view characters. With this technique, you confine yourself to one character's perspective in each scene. So the reader only learns about that character's thoughts and feelings in that scene. You can only switch perspectives when you switch chapters.
So to summarize...
1. Decide where the camera is and stick to it within a scene. If it's inside one character, keep it there. If it's like a moving drone (omniscient), stick to that. Even if that drone can peer into characters' minds, be consistent so you don't confuse your reader.
2. If you can't do that, consider a different narrative mode.