Ok, I think it’s really fixed in the latest beta version.
It was trying to build up a folder structure because the Drive plugin used to be able to get all files in Drive, not just the ones you choose. So for some items in subfolders it didn’t have permissions to access the full folder structure, so it never showed those items. So now it will just load all items regardless of folder structure, and so you should be seeing every file you selected now.
It still seems to sometimes not update immediately after selecting a file, but it does after refreshing the page. I’ll fix that in the next update.