I remember watching House of Flying Daggers years ago. I was getting into the political story about rebels and assassinations but then half way through it turns into a love story. That love story then plays out and reaches a conclusion...and then the film ends. What happened to the story you started with? I was quite enjoying that. I have nothing against a love story but don't bail out halfway through a film and start making a completely different one.
A similar thing happened in The 39 Steps. As much as I love the film it forgets all about the plot about two thirds of the way through and instead focuses on the relationship between the two leads. At least Hitchcock realised this however and spent the last five minutes of the film rapidly wrapping up all the necessary plot points.