As I say in my books, that's how the program (and virtually all video editing programs) create transitions. It needs head and tail material to create the transitional segment.
I believe that what you are running up against is a lack of Handles. These are Frames past the Out Point, or before the In Point, that are needed to complete a Transition. These images should help you get a "handle" on Handles (pun intended).
Before one was able to do single Track editing, and relied on A-B Roll editing, Handles were easy to both see and understand. When Clips were all able to go onto a single Track, the Handles were not seen, but were no less important.
Just adjust your In & Out Points on your Clips to accommodate the Duration of the Transitions.
Good luck, and hope that helps.
Thank you Bill that exactly what I ran into. I will adjust the clip like you said.
Handles are a bit abstract at first, unless one comes from film (like me), or from older video editing programs, where A-B Roll layout was part of the workflow. They trip up many, hence my (and Steve's) images and links. We see it quite often.
For others, this is why one starts the camera recording a few seconds before any defined "action," and keeps it recording for a few seconds after all defined "action" has completed - Handles for Transitions.
When I run into a situation, where I, or a client did not allow for adequate Handles, I will often add in a bit of Black Video, and then do Dip-to-Black Transitions to hide the lack of Handles. That limits one to only one choice, but will often effectively get a Transition in place, rather than a Butt Cut, though that can be very effective also. Depends on what one wishes to convey.
For me, I use Butt Cuts often, and then Cross-Dissolves to indicate a short time lapse, or perhaps an angle change in the footage. I then use a Dip-to-Black to show a longer time span lapse, or perhaps a major change in location. Just my aesthetic choices.
Good luck, and happy editing,