QubesOS Exception Handling, Memory Issues, Debug Flag/Mode

How would the devs describe the level of exception handling in Xen/QubesOS. I find that crashing happens
quite often and there is no exception thrown to the user for debugging.

Will QubesOS crash due to memory related issues? Is there error message for insufficient memory? Or will it just crash.

Is there a debug mode for Xen/Qubes? Are there Debug flags?