"falls through" is a phrase used to describe something that doesn't happen as planned, often due to unexpected issues. There are many synonyms for this phrase that can be used in different contexts. For example, "falls apart" refers to something that breaks down or crumbles, while "fails" means that something was not successful. "Collapses" suggests something that suddenly and completely gives way, while "disintegrates" implies a slow and gradual decay or breakdown. Other options include "comes to nothing," "fades away," "dissolves," and "breaks down." Each of these synonyms can help convey a different nuance or tone for describing a situation when things don't go as planned.