Purple line at bottom of clip

I get a purple line sometimes at the bottom of my clip, which I can adjust with my mouse (though I don’t know how to use it and don’t want to use it. Only way I have found to remove it is by removing my effects. How do I avoid that being implemented in my clip and getting rid of it?

Can you help us help you by stating OS and version of Kdenlive, and whether you installed it (how?) or use the appimage/standalone?

and also what kind of clip… because in the past this kind of issues was about PNG transparent images.