Just letting you know from past experience that 1.05.0021 is not a version you should use for the ability to rollback firmware. When we did the beta 1.04.0008 it was the very last version were given to beta test. And both the android and iOS teams had finished with the 1.04.0008 being super rock solid. That version was tweaked to perfection, and the beta project stopped. I personally was so proud of what we had accomplished considering how messed up 1.04.0002 we started with was prior to. Then the day after they published 1.04.0010 firmware which was untested, and the android and iOS users both were having video reception issues as well as other stuff. That for me was a sad day. I loaded the 1.04.0010 because it included something to do with the app displaying one of the new features. In doing that, I then also had the **** video issues. I then tried rolling back to 1.04.0008 and it said I was trying to load the same version. Prior to all this I use to be able to load 1.1.9 FW but was no longer able to. To make a long story short, eventually the 32 channel mod saved me. This all took place with my Nexus 7 2013 version.
And now, updated R/C firmware, app 2.4.1, firmware 1.05.0021, and the 32 channel mod all installed and I have poor video with a little lag.
I don't know if you are still beta testing, or if you stopped when the firmware project ended, but they now say the processor and ram speeds need to be about double of what I have in the Nexus 7 2013.