Scorchy,
Add this to your things to try. When you begin noticing you are leaving the 7 pin, look to see if you are coming high or low on the head pin. If you are coming high on the head, take about a 6" step forward from your normal stance and throw your same ball.........speed, mark and hand rotation. If you are coming in low on the head pin, then do the reverse, 6" step back and see what happens.
I can get in a rut with 7's or 10's and make that little adjustment and it helps. Hope this helps.
Live long............bowl strong.
Terry