Some users faced this problem while publishing simulations in Adobe Captivate: the preview is displayed perfectly; however, when the video is published to MP4, it shows distorted slides or overlapping parts. There are some causes and possible fixes.
To fix this, go to Adobe Captivate ”Edit” menu > “Preferences” > “SWF Size and Quality”, move the slider down to “Custom” and deactivate the two options of compression.
According to the manual:
Advanced Project Compression Enables Adobe Captivate to take into account only the difference between two slides instead of publishing both the slides. The compression reduces the size of the published project. Choosing this option can increase the time taken to preview or publish the project. Compressed projects sometimes do not play as intended in Flash Player.
Note that this might happen if you work mainly with Adobe Captivate native components; however, if you have rather included an external video, you might need to think differently as it might be a decoding issue, and it might be solved by using a decoder to re-decode the imbedded video before importing or the whole resulted MP4 video after publishing.