I too have been having this issue. If I were to guess I would say it started after MS updated my machine to Windows 10, but I am not positive.
I'm running Windows 10 on my laptop and it's ok on that.
What model of camcorder is your video coming from and what format and resolution is it?
Do you have the latest version of Quicktime installed, per the program's requirement?
What do you see under Project Settings under the program's Edit menu?
Two gopros - .mp4 and a Zoom camera -.mov
Yes, latest version of Quicktime
General - DLSR, 25fps
Capture - DV
Video render - Max bit depth unticked, Optimise Stills ticked
Thanks for the reply
Ah, now I do have yellow lines above the .mov file. But not the mp4 files. It's stopping even if I remove the .mov file completely from the project though
It's the first clip on the timeline that determines your project settings. Is there an "render" line above the first clip?
Do you see improved performance if you render your timeline (by pressing the Enter key)?
No and No, rendering makes no difference!
Something is up with your system. Unfortunately, I don't know how to troubleshoot it on this forum.
Maybe someone else will have a suggestion.
OK, for anyone with the same issue. I solved mine by changing away from the Realtek onboard sound device. I've just run through the same video for an hour with no stops.
I know that Realtek has caused issues in the past from my reading on this subject and it has certainly proved the case with me. It's a terrible sounding device anyway, so moving my PC audio on to the sound card that I normally reserve for my recording studio work is a bonus.