Just did a 1600 mile road trip, kids got an old iPad I preloaded w/movies.. had a couple of issues I thought worthy of reporting.
First of all, I stuffed the tablet w/movies.. but had 2GB free.. We kept getting notifications of low space, so we kept deleting apps/photos and even downloaded movies off the tablet and then Emby would consume all the available space for no apparent reason.. if I got 4GB free, within a few hours we were getting low space notifications and emby had grown in data size by that amount.. I dont really understand why Emby would consume free space watching offline media but it seemed we got no relief and just had to deal with the errors interrupting video playback.
The second issue I had was that Emby at some point had crashed hard (maby filled up all space?), required a hard reset of the tablet.. when it came back, it had lost its user credentials and would not permit us to access downloaded media.. It was not until we found some Wifi, and I got it logged back into my Emby server that we were able to access offline media.. IMO, if this situation happens offline media should still be available.