I’m not sure if this is the answer, but are you looking at “courses” instead of “lessons” when on your lesson page? generally when I import longer content thats how I find them. this is right above your lesson list.
Thanks. Yup, looks like only part 1 got imported in your case. I just tried on my end with Chrome extension and complete video got imported successfully, all 3 Parts.
Which browser/extension are you using? Can you please give it another try?