Hi Gideon, thank you for your report. Initially I thought your issue was caused by a missing access files permission, but while troubleshooting it we’ve found something wrong. It seems our framework gets a wrong answer when querying Android about what is the root folder the app has access to, and this happens not just in the sandbox but in any folders tree. We’re still investigating it, but we’ll be sure to include a fix in the incoming app maintenance.
Until then you can work around the issue by opening app settings and by tapping the “Reset default settings” link. Since the application has the “all files” access, it will detect again the default transfer folder and set it to “Download”, which is more comfortable to move your files before uploading them.