I am having a similar problem (every 5th and 6th bulb on green ring wont light) except the bulbs that don’t light on ours are a little different.  On the end of each row of 6 bulbs is a little tee pee / pyramid shape.  Those 2 bulbs on eith side of this shape all the way around are the ones that wont light…ideas?  thanks for help me and my boys were doing so well up to this point.  We are frustrated!