Moodle in English

Has anybody out there tried to enable an Assignment submission plugin for MoodleMobile? From what I can tell while this is supported using the "Templates downloaded on login and rendered using JS data" method, but only the core submission plugins have been done and they are directly integrated with the app and I'm struggling to relate that to how I would make a 3rd party submission plugin work using the template download method. I have been looking at this: https://docs.moodle.org/dev/Creating_mobile_question_types which at least gives a complete example of how the template download technique works, but a few more good examples would be useful. I've gotten to the point where MoodleMobile seems to recognise the presence of the submission plugin, but it won't render anything, I just get two spinners saying "loading" overlayed on each other. Also, when testing with the app on a real device, what's the most reliable way to ensure the plugin code sat in the app is updated from the server? When I last looked at this I couldn't get past the stage where the app was showing a message saying my submission plugin wasn't supported, despite clearing caches in Moodle, bumping the version number, deleting user data in the app and re-syncing in the app. Having left this for a week and come back to it, with no code changes the app is no recognising my plugin as supported (but not working). So something was stuck in a cache somewhere in the app that I couldn't clear.