Hi Rizman
Also not quite sure what you mean by "Less than 1-2 min" and "auto-populate" However switch the timeline into Storyboard mode and check that you don't have a blank "frame" where you have split the clip and want to add the transition. (There would be no "X" in any case.) It's just a thought. There were some reports in earlier VP versions that a split caused a tiny gap in the project that was unnoticeable at normal zoom levels.
Are you overlapping the clips or choosing to add a still frame? Obviously overlapping means that there must be adequate final clip length to accommodate the length of the transition.
Could you clarify the problem.
Nat