Subdivide modifier issue

Hello all, I’m having a bit of an issue at the moment with the subdivide modifier. I want to add more detail to a specific part of a mesh by making it rounder, and it does, but it also causes a different row of faces to distort. Ill provide pics below to better specify.

if anyone knows of an alternative method to achieve this without distorting those faces, or if anyone has a fix that will let me just use the subdivide modifier, i would much appreciate it.

maybe use the crease option in edit mode for subdiv at that edge loop.
Or bevel the edge or inset the inner poligons of the shield a very little.