It could be that Levi is injured. In many fanfiction scenarios, the character might have sustained some sort of injury that affects his ability to get on the horse. For example, a leg injury would make it physically challenging to mount the horse.
Another way the plot could develop is that his inability to get on the horse could be a sign of a greater conflict. Maybe there's a war coming and the horse is a key part of his battle plan. His comrades might start to doubt him, causing tension within the group. This could lead to internal strife and Levi having to prove himself in other ways while still trying to figure out how to get on the horse.
In a fanfiction, Natsu might get angry if he was wrongly accused of something. Say, if he was blamed for a crime he didn't commit in the guild or in the magical world at large. He's an honest person, and being falsely accused would be a huge blow to his pride. Another possible reason is if a magic - based experiment went wrong because of someone else's carelessness and it put his friends in danger. Natsu values the safety of his comrades, and such a situation would make his blood boil. Also, if someone were to try and break up the Fairy Tail guild by causing internal disputes, Natsu would be enraged as he loves the unity and spirit of the guild.
There could be several reasons. Maybe the website is experiencing technical issues. It might be under maintenance or having server problems. Another possibility is that there are copyright issues preventing the release. Some fanfiction may violate the original work's copyright terms, so it's not made available.
In some fanfictions, Dumbledore might get punished for his past mistakes. For example, his actions regarding Tom Riddle when he was at Hogwarts could be seen as negligent in hindsight. He might have missed signs that could have prevented Voldemort's rise, and the wizarding community in the fanfiction could hold him accountable for that.
In fanfiction, the Dursleys could get arrested for child abuse. They treated Harry Potter horribly, locking him in a cupboard, underfeeding him, and constantly berating him. Another reason might be for illegal use of magic items. If they got hold of some magical objects through Harry and misused them, that could lead to their arrest.
One possible reason could be his fear of losing his independence. Harry has always been a bit of a lone wolf, used to relying on himself. Marriage might seem like a threat to his freedom to do as he pleases.
Well, it might also suggest that the wife, while drunk, is so into a story that she doesn't want it to end. It could be a story that has some sort of emotional connection for her, like a love story that reminds her of her own relationship, and the alcohol has made her more fixated on it, so she just can't get enough of it.
In the fanfiction's world - building, there could be a cultural or religious group in the wizarding community that Harry has become a part of, and they have a strict no - meat diet. This newfound identity or connection has led to him not being able to eat meat.
It could also be due to differences in their beliefs. Brasidas is a Spartan, with his own set of values and loyalty to his city - state. Kassandra, on the other hand, has a more individualistic view having traveled far and wide. Their different outlooks could lead to a clash. For example, if there was a decision to be made about how to deal with a new threat in the region, Brasidas might want to handle it in a traditional Spartan way, while Kassandra could have a more unorthodox approach.
It could be that he ate something bad in the story. Maybe some spoiled food from a dodgy tavern in the fictional world.