The problems are also inconsistent unfortunately.
For example I've just restarted my iPad, gone into Files, Dropbox, downloaded the file I want (ie. clicked on the little cloud icon to get it to download locally). Opened StageTraxx, created a new multitrack file, tried to add the file in the multitrack setup via the Files browser, but as soon as I clicked the file StageTraxx closed unexpectedly. Reopened StageTraxx, had a look at my multitrack song...and the file is listed in the multitrack setup screen. So the import worked...but crashed StageTraxx.
These are large wavs (40MB), 16bit, 44.1KHz. I have a large amount of files and folders in my Dropbox, and quite a few levels of nested folders...not sure if any of that makes a difference?