Are plot holes in novels common?

One common plot hole could be when a super hero has powers that seem inconsistent or conveniently change to fit the story.

Since I don't know the exact 'holes story', I can only guess. Maybe the main plot is about a character who is on a quest to fill holes that are causing problems in their world. For example, holes that are swallowing up important things like crops or buildings.

One possible plot hole could be the time jumps that seem a bit inconsistent in terms of how the events are connected. For example, the sequence of the briefcase's journey and who has it at different times can be a bit muddled.

No, not really. I've hardly ever heard of 'paddle holes at school' being a common theme in typical school stories. Most school stories focus on things like friendships, academics, or school events.

Cartoon black holes often have a dark, swirling appearance and a strong gravitational pull depicted with lines or effects.

Take 'Cinderella'. The glass slipper is a major plot point. But think about it, how could a glass slipper fit only Cinderella's foot so perfectly in the whole kingdom? It's a bit far - fetched. Also, when the clock strikes twelve, all of her things turn back, but the glass slipper remains. It's not very consistent in the rules of the magic in the story.

Plan your story thoroughly before you start writing. Make sure all the elements fit together logically. Also, have beta readers review it to catch any potential holes.

Maybe the story is about a cave with 10 holes. Each hole leads to a different level of hellish nightmare. A group of explorers enter the cave out of curiosity. As they peer into each hole, they see visions of their worst fears - for some it's losing their loved ones, for others it's facing their own mortality. And as they move from hole to hole, they start to lose their sanity.

There are a few plot holes, like some character motivations that seem inconsistent or unexplained.

Well, themes like curiosity and exploration are often seen. Sometimes, it could also touch on forbidden or taboo subjects.