MATLAB PDE solver residual

My task at hand is computing the deformation of thin metal plates made of steel due to self-weight.

Load: self-weight (gravity)

BCs: Elastic (rigid) BC at certain regions on the upper surface i.e. applying high artificial stiffness.

Geometry: can be arbitrary with thickness 2mm.

Problem: I have created an automated way to run the FEA for different kinds of geometries, but unfortunately in some FEAs, it gets stuck in the "nonlinearsolver.m", due to the residual still being greater than the tolerance.

Could someone please suggest if the issue is related to the size of mesh, BC or any other limitation of the PDE toolbox?