handling thin geometries and convergence problem

Hello,

I am trying to simulate Joule Heating analysis for a very thin geometry (description- 3 domains over each other with different materials respecectively,each have certain thickness) Please check the the attached file!
In Joule heating module, I am assigning HEat flux to respective boundaries of interest. (Basically a heat transfer problem) The physics and mesh is all set.
However when it starts computing it shows the following error at a certain time step.
"Nonlinear solver did not converge.
In segregated group 1:
Time : 0.8
Size of vector and sparse matrix disagree.
Last time step is not converged."

May I know how can I resolve this issue?

Many thanks!!