When you remove some clips in the end of your project, kdenlive automatically shrinks timeline length. But it do not cares of remeining transitions at the end of project. Video how to reproduse included (youtube link). This situation may happen when you remove a video clip, which is wider in timeline then your screen may display. So, when you render the whole project, in your result video file there is a long black tail. Suggestion: we should be able to place play head to any last object in timeline, even if it is just a transition.
It seems that this report is related to very old unmaintained version. A lot changed since then, especially the timeline got a complete rewrite and it is likely that this has been fixed. Feel free to reopen this bug or create a new report if this is still happening with the latest version (https://kdenlive.org/en/download/)