The alcohol fallback scene usually involves some form of the following:
One of the characters gets drunk and does something horridly stupid (yet entirely expected, because they're drunk), such as kissing and/or sleeping with the exact wrong person.
Or maybe they just make a complete zebra of themselves and the other can't handle it.
I'm not saying your characters shouldn't have problems or shouldn't break up at some point. That's actually pretty standard in the romance plot, and most romances don't work without some kind of split at or around the 3/4 mark. It makes the getting-together-at-the-end all the more satisfying.
What I'm saying is that using alcohol as a means to incite a major turning point in your story has been done to death already.
Stop doing it. You're more creative than that. Think up something better.