It’s very common to have stress singularities in a model. An example is a sharp interior corner. If an interior corner is the location of the maximum stress, you can modify the geometry and blend that interior corner with a radius. Locally mesh that new blend face with elements small enough to put at least two elements across the new blend face and the stress will be reduced. There are many other ways to create a stress singularity. Please reply with an image of the mesh where the maximum stress occurred.