Above the complete video file (with audio) Jaksta records a separate Video file and a separate Audio file.
It's annoying because one recording takes doble the space on my hard disk.
Do you actually see the separated audio and video files in the Jaksta list in addition to the combined file? Are you able to send us a screenshot of what you see?
The next time this occurs, can you send the log file to us? You can find it by going to File|Reveal Log File... in the menu.
Jaksta often has to download the video and audio parts separately and combine them at the end. But it should not leave the separate parts behind afterwards.