Hi Hyun,
When that error message comes up, it could be related to the actual sketchup item. It is possible that the item itself is damaged. Although I have been playing with Sketchup for a little bit now and have found that this error messages presents itself more when trying to import a 2020 model.
What I would suggest is, instead of trying to import 2020 models, simply import 2019 models and you shouldn’t come across any other errors.
Regards,
Kris