I'm getting a battery error which might just mean low battery:
https://www.reddit.com/r/kindle/comments/5a6z6c/your_kindle_need_repair_battery_invalid_22/
Where does that solution come from? Or, does the invalid battery indicate loose connection? It's outside warranty, but only a few months old. Might be within ninety days. Right now I have it charging but try the suggested empty file trick to see what happens...