Scripting: can't make MovieImport work

Hi there.
I can’t make MovieImport.doImport work. My script terminates with a generic error “QuickTime movie import : An error occurred while importing the QuickTime movie.”
The images are correctly extracted in the directory set by setImageFolder,
My goal is to mimic by scripting what performed by File->Import->Movie, which works fine with the same input movie file used by my script.
Using Harmony 21 Premium.
Attaching the screenshot. Thanks.