Try to set the bit rate to, say, 1.5Mb or 2.0Mb. It worked for both my Samsung S8 and Redmi 5 plus.
I just picked up a Tello, and have had some problems with the saving of photos and videos. When I take a picture or video, it acts like it takes the picture or video, but doesn't save it. I have tried restarting the phone, checking the "play" button, and checking the gallery. I also tried plugging it into my computer, but Windows 10 wouldn't recognize (or detect) my device. I have moderate drone and computer experience. (Except for the Tello, got that 3 days ago.)
--- Samsung Galaxy S8
--- Android Version 8.0.0
--- Kernel Version 4.4.78