Can't move video clip flush against other video clip

In Adobe Captivate 8 I have two video clips next to each other on the timeline. There is a gap between video clip 1 and video clip 2. I can't make video clip 2 go flush against video clip 1 (move it left), however it moves further away to the right. What do I have to do in order to make video clip 2 sit flush against video clip 1 in the timeline?

Thank you.