The Freeze Subdivision Levels feature is basically designed to let you make changes to the base topology even after sculpting in a few sub-d levels of detail. For instance if you realized you needed more geometry on an arm then you could freeze it, add a few new edge loops, and then when you unfreeze the model it will automatically subdivide and project the original detail back onto the new mesh.
The problem you’re seeing is based on your mesh not being symmetrical. So when you unfreeze, it’s sort of like trying to project the shape of a “d” onto the shape of a “b”. It’s a mismatch.
Rather than freeze the subdivision levels, you could just delete the lower levels. They can be reconstructed afterwards. Alternatively if you’re just looking for a quick preview then you could also use Array Mesh to mirror and offset an instance of the tool.