First, Check your project settings & the original video format: are they compatible? Is the original HD or SD- make sure you export the same definition (the max for SD is 720 for best quality). You may need to go into your 'advanced' setting dialogue and make sure the export does 2 passes when rendering out. See if those work out. If not, I would say it may be a bug fix that is needed, which I'm sure Magix will do very soon. Be well!
You should not need to use 2 pass, just check that the export template you use is the same resolution and similar bitrate as your original video files.