Developing good characters is an important part of the writing process. Without them, any novel is going to suffer. And, if it does, then people are going to have trouble reading what you've written, or, worse still, they won't bother reading it at all.
The 'down side' of having good, well-developed characters is that sometimes they won't do what they're told.
You have an idea, you have the characters, the locations, the obstacles, the plot, and everything else worked out, and things are looking great. Until your characters decide that they'd really rather not do what you want them to do.
I can hear people saying "but they're your characters, don't they just do what you want them to? It's not like they have a say!". If only it were that easy.
Sure, you can force characters to do your bidding, but you run the risk of it feeling forced. You risk the all important suspension of disbelief being broken, and the reader going "hang on a minute...". And that's bad. I've read many novels where I stop reading, and start thinking not about what the characters are doing, but why the hell they are doing it. Why they are acting so out of character. It leaves the over-all reading experience lacking. You want the reader to be immersed in the world, the characters, and so forth, not questioning things (unless, of course, that is the kind of novel you're writing, but that's not what I'm talking about here).
So, the best solution, is to let the characters do what they want. To hell with your best laid plans - let the characters be the characters that you created, not force them into some situation, or action, that they wouldn't do. They might get back to the track that you have waiting for them, or they might lead you on your own merry adventure, as they explore their options and your world the way a real person would.
At the end of the day, I think this can make for a better story.