Try ffmpeg from the command line and see if that works for you. See https://discuss.eroscripts.com/t/how-to-get-started-with-scripting/2234 and go down to the section called How to improve performance when stepping frame by frame in JFS.
This is the interesting part:
Use the following command line after changing paths and video file names:
“C:\ffmpeg\bin\ffmpeg.exe” -i “C:\MyScriptingFolder\source_video_file_name” -filter:v “scale=2048:-1” -intra -qp 30 -acodec copy “C:\MyScriptingFolder\desination_video_file_name.mp4”
Change the path to where your ffmpeg.exe is located.
Change the path and file name to the file you want to convert.
Change the path and file name of the output file.
If this doesn’t work then something is really fishy with your computer.