The connector in the tablet isn't soldered down to the board completely. One or more pins isn't/aren't making contact unless you "twist" the connector just right. If it's still in warranty have it exchanged. If not you're going to have to find a shop willing to work on it. It's not difficult to resolder the connector, but there's no shop manual available for these "no name" devices, so opening it could damage something, and the shop would be responsible for fixing it, so most of them wouldn't want to take the job. (And you can buy a new one for less than anyone will charge you to repair it. They have to include the possibility that there's a "gotcha" or two in opening it in the repair price. $75 would be a cheap repair price, and they sell for about $60.) If you know an electronics hobbyist, he may be willing to try to resolder the connector for you.