Choppy mp4 output

[fugge Profile Private message]

I have a show based on an mp4 video file.
When I publish this as a YouTube 1080p mp4 file I notice that it is partly choppy. It looks like it "jumps" like it is recurrent skipping some frames.
When I publish as YouTube 1080p60 it looks a bit better.
The source video mp4 file does not have this behavior.

Any idea why this is happening?

Proshow Producer version 9.0.3776.

/Fredrik