@martinithyme
I swear sometimes posts on this forum are hidden from me because I check every day and never saw this until now. I don’t know what’s up with that…
Anyway, if you’re on Windows I’d suggest using ShutterEncoder and converting all your files to hap.avi. Sometimes video files can be exported with strange settings that Isadora doesn’t like (for example, embedded timecode tracks have been known to cause playback issues).