Is this a pre-lateral adjuster Stanley? You mentioned you are novice, have you set the lateral adjustment of the iron?

I haven’t run into a “rocking” frog personally. My next step would be to examine the underside of the frog and the bed for damage. You may have a small burr somewhere that is interfering with the frog seating. If yes, you should be able to file the damage away fairly easily.

It’s possible the plane body and frog are from two different planes and aren’t a mated pair. Inspect the frog and bed and confirm both are flat.