Convergence problem

Hello to all,

I'm trying to simulate signal transfer through human arm. At the moment I'm facing convergence problem and I really don't know what to do. I tried to change model boundary conditions and solver type (all iterative and direct solver types) but nothing seems to change.
I know that there is no use of these few words so I attached my model.

Any help would be most appreciated!

Thank you very much,
Josip