Google Drive just lists the first 100 items of a folder
Since the Google Drive implementation does not support paging and default pages are limited to 100 items, the app lists the first 100 items of a folder only. There is a commented hack in the code to raise the page size to 1000 which should mitigate the issue for 99.997% of our users without going the extra mile of implementing paging.
This is a rather common complaint on the App Store about our Google Drive implementation.
To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information