Differences between Overlap transitions and Cut transitions
Problems with using Overlap transitions are mainly caused by users who are accustomed to using Cut transitions (so-called Seamless Transitions) from legacy Motion Bro products. The problem lies in the misunderstanding that these are completely different types of transitions, both technically and visually. Here is the main differences:
Overlap transition effects transform the content only for the layers selected in the timeline, so you need to select both layers that you want to connect through the transition. This approach has a huge advantage: during the transition, you can simultaneously see the two scenes IN and OUT that you have connected.
Cut transitions are created from a group of adjustment layers and it’s effects transform all content below the transition layer. Thus, you do not have to specify the layer on which you want to add the transition. You only need to specify a layer so that the transition is added to the desired timing along the timeline. This is convenient, but at the same time it is a disadvantage: during the transition, it is impossible to display the IN and OUT of the scene at the same time. You can only see the initial IN scene up to the Cut marker and then, after the marker, only the final OUT scene.
Transition only affects one layer
Before you apply the Overlap transition, make sure you have selected two layers in the timeline that you want to connect through the transition.
Transition only affects the second clip. Solution One
Perhaps the duration of the first layer ends before the transition ends. In this case, the transition effects have nothing to transform since there is no image.
Make sure that the duration of the first layer does not end before the transition ends.
Transition only affects the second clip. Solution Two
Perhaps you are using a single layer that consists of several footages. If you just cut such a layer at the junction of two footages, it will be a problem for the overlap transition.
Make sure the first layer is a single footage, with enough duration after the cut.
The first layer is footage that cannot be extended any further
In this case, as a workaround, you can freeze the last frame of your footage. To do this right click on the footage and select: Time > Freeze On Last Frame