Hi Nils, just realized: you can also trim the video using the menu when you right-click in the sample display of the clip (see below). Did you do that? When you do that, Ableton will create a new audio file and will replace the video with this newly created audio-only file (just like when reversing a file, see above). The video will be lost then. There are a few ways to crop the video clip without this issue, see here: Cropping start and end points - #7 by Jeroen
