debugger doesn't work in chrome / safari/ firefox for ember app

I am working in an ember application. The version is "ember-cli": "1.13.13".

For a very strange reason, debugger doesn't work in Chrome. (I also tried Safari, and Firefox developer's edition. Same thing.) Specifically the problem is I put a debugger statement in a function. Ember app loads and hits the function and the debugger statement in the function. What happens in the Developer Tools -> Sources tab is that it doesn't show me the function that the debugger is in. Instead it keeps highlight the last line of app-boot.js file. The breakpoint, or the line that it's paused on, is not showing up at all. (see screenshot attached)

Furthermore when I step into the function call using the down arrow, it remains at app-boot.js, so I have no idea whether it did step into the function or not.

This has been plaguing me for a while now. Any help is hugely appreciated.

Screenshot. Click me