I am about to start writing a fantasy-comedy novel. A problem I found in 1-2 books of this genre is that the plot becomes weak, and the story starts to slow down.
The reason I believe this happens is that there is no big struggle or evil villain. Since there is no tension in the plot (as it is a comedy book), the plot soon loses focus. The story breaks down to "Hero goes to place A, does something funny, then goes to B, does something funny" etc.
How do I avoid this problem?