What is your operating system?
What is your Shotcut version (see Help > About Shotcut)? Is it 32-bit?
Can you repeat the problem? If so, what are the steps?
(Please be specific and use the names as seen in Shotcut, preferably English. Include a screenshot or screen recording if you can. Also, you can attach logs from either View > Application Log or right-click a job and choose View Log.)
I’m editing a long video, currently have 2 video tracks, and 1 audio track, copy a clip, move clips around, Ctrl+v, click properties, lower speed, click play button, shotcut shows clip has been slowed (it is longer in track), then program closes.