It is most likely experiencing a conflict with the Mac OS, as we never built any support into any of the Version 1 builds for High Sierra before we stopped development on it.
If a full reinstall is not helping, then there are really only two options. Downgrade the Mac OS to a compatible version or upgrade Jaksta to Version 2.
If you have not yet tried a full reinstall then use the following instructions:
Delete the app (uninstall) from Applications instead of just reinstalling over it. Then in Finder go to the top menu and then access Go > (holding one of shift/alt/control/command) Library > Application Support > Jaksta Media Recorder and delete that folder (NOTE: doing this will erase your library file list in Jaksta, but your downloaded/converted files will remain intact in their destination folders). Reboot the Mac and then do a reinstall of the latest version (https://www.jaksta.com/download/mac/jaksta-media-recorder) and it will generate a new copy of the deleted folder and the application files.
Please let me know if you need any help or more information on upgrading to Version 2.
I have upgraded my Mac to OS 10.13.3. When I open Jaksta Video Recorder 1.5.1, it seems to open successfully but when it detects a video, it quits with a dialogue box saying "Jaksta quits unexpectedly". I have tried re-installing Jaksta but no use. What can I do to resolve this problem? Many thanks!