It isn't immediately obvious to me why ode15s is terminating prematurely. pdepe problems of this complexity often require considerable effort to debug.
I do not know whether you will be able to accurately model the interface jump conditions using pdepe. But you should update the description of your model to include these jump conditions, the boundary conditions, and the initial conditions. I can say for certain that the approach you have taken to account for the jump conditions will NOT work.
Beyond that, I suggest doing the following as initial steps to debug this:
- Create the mesh so that you have mesh points exactly at the interfaces.
- Remove the jump conditions from the model and see if pdepe can solve that model.