Nios II exception handler

Hi,
I'm using Nios II and experiencing some strange behaviors.
1. Sometimes the system gets stuck.
2. The system resets.
3. In debug mode - the software get stuck after going to a trap.

The Hardware is Altera's Cyclon3 with Quartus 12 SP2.

In order to better understand the problem I want to try and catch exception with exception handler.

I'v enabled hal.enable_instruction_related_exceptions_api in bsp editor, implemented and registered the handler.

The handler does not work the way I expected it. It is not triggered at all.

How can I test it? Do I need to add something to the hardware as well?

Thanks