If you are describing what happens when you are on the nose, sliding across the wave:
I don't think it's fin related.
You are probably digging in your waveside rail, climbing up the face and over the back.
The fix is something I learned watching Mikie Dora noseride.
Use your knees and ankles to tilt the beachside rail down the face, to release the inside rail.
the board will slide lower on the wall.... then simply re-apply subtle pressure to the inside rail to stop the slide, and begin tracking across the face.
All done without moving your feet on the board..... just simple manipulation of the rails.
This video shows me climbing and dropping on the nose, with just subtle moves ankles and knees.
Sorry for the pimping, since this is an introductory look at the 10' Style,
but it's the only vid I have, where the rail control is easy to see.
Skip to :55 secs to avoid the intro
Watch my knees do all the work, while my feet stay planted
Odd thing for me is... I find this much easier to do backside.
I have much better heel-side rail control when noseriding on my backhand