I can’t reproduce this on an empty project, all I can tell you is my project file is destroyed, and all I did was add an additional clip to the end of the time and change its speed.
I added one new clip to the end of my timeline, and set its speed to be 10x faster, in the properties dialogue. Soon after I had already saved multiple times, I realised every single clip in the timeline had been sped up, even though they are from completely separate video source files and sound files. This has ruined all of today’s work, since there is no way to undo this mess. So many carefully timed sound effects and video clips, all ruined.
I can’t even work from the project file to resurrect it, as even the clips I drag from the playlist, seem to have been permanently shortened. I have to go back to a previous project file.
Shotcut version: 19.02.28
Operating system: MX Linux
I found a related bug: