After applying transition in Final Cut Pro, the first frame of following sequence will flicker.
I selected the clip in the timeline and then went Cmd9 to reveal the properties > it turned out that if the original clip was compressed using the H.264 codec then the outcome will definitely flicker after I apply the effect (say Dissolve) when rendered. It turned out that "H.264 is not a production codec and should not be used in FCP. The media should ideally all conform to the same format as your sequence; you certainly should not be using a codec that is based on interframe compression like H.264. That's for acquisition and for delivery, not for production."