I think before some of the more knowledgeable bowlers here (not me) can help you, they are going to need some more information on you.  Most importantly, are you RH or LH?

A lot depends on you style.  I am a long, slow four stepper, and when my feet get a little fast one of two things happen.  If my arm swing stays in pendulum I will miss right.  If I muscle it to catch up with my feet I will miss left. 

If you are right handed, dropping your shoulder(just one among many things) could cause you to miss right.

Brad

Second that. Check your balance at the foul line - it might either be a sluggish body posture, which lets you drop your shoulder, and/or some footwork issue, maybe slightly fast feet, so that you have to move your upper body and compensate for the lack of overall balance - in a consequence, you keep your hand too long in the ball, and you follow the swing with your whole body. Maybe just straightening your shoulders and keeping an "chin up" attitude solves the problem.

Also, how open are you in your stance, before you take your first step? Are your feet parallel with the boards, or pointed towards the right gutter?

Check to see also how open you are after you throw a shot, take time to not move after the shot and look at your slide foot in relation to the boards on the approach-ie is it parallel with the boards, or is your toe pointing towards the right gutter?