The headset is not fully compressed, push the starnut in more
omg are you using distric ics or normal long bolt?
its because your just fucking threading the ics into your starnut and the end of the bolt is not pressuring against anything so its not tight. if you using a district fork you NEED to use a district compression. or you can hammer the starnut waaaaaaaaay into your bars.
then your not doing something right.