Breake in a dialogue

I have a dialogue where two people talk too fast. I did slow motion in Sony Vegas and now I would like to add 0, 5-1 sec of silence in between the words.

I'm doing the following:
splitting the movie and the audio
taking a snapshot of the last frame of the first split segment
and then I would add that picture of the snapshot on the video frame and repeat it for 2seconds
then I would split the second segment one more time where there is only noise and nobody talks
I would then copy the audio with the noise on the timeframe under the snapshot taken before

but if I do the above and play, the image is fine, but at the end of segment one you could hear a click between the audio of segment 1 and the noise that I've copied, it's not continuous the sound.

What do you think, what am I doing wrong, or what should I do better.