Modelling fiber lasers in Julia as a BVDAE problem

Hello, I am trying to model a fiber laser using Julia. I’ve managed to simulate an amplifier which is an initial value DAE problem, now i need to extend the code to a BVDAE problem to handle different laser resonator architectures. I’ve read the relevant documentation and based on it tried to use the Ascher method however the solver does not converge. Code fails before that, when setting up boundary conditions (I think). Below is a working example, since the system is stiff I attach all variabl...