Sometimes videos are rotated or they appear upside down after processing them. This happens when there is issue with the metadata of the source videos.
In order to resolve the issue & repair the metadata on a Mac, please follow below steps :
a) Double click to open the source video in QuickTime player.
b) In the QuickTime, please go to File -> Export as -> 1080p (or click on 720p) . Please see the below screenshot
c) Select a location to save the Video. This process will repair the metadata of the videos and you will be able to process them using the application properly.