Just took my new radrunner for a very short ride, about 10 yards.  I have the exact same problem and got the same bad advice from customer service.  There is something wrong with the hub sprocket.  Chain and tensioner are fine and aligned properly.  Pedaling with moderate force especially on a tiny incline causes a slip.  Bike is at an authorized repair shop on Day 1 with no usage due to this slippage issue.  Unbelievable.