When there is a block directly at the bottom of the Dream Focus: Fluid, and then using the Focus to set the route, the process will continue even after the timer has already been counted down.
So far as I know, the only way to stop the process is to interact with other devices (such as Dream Foucus: Villager and Dream Foucus: Item).

Some people had been reporting an "infinite pathing" bug for Dream Foci and I couldn't figure out how to reproduce it, so I am extremely thankful for this. Just fixed it in this commit of the development branch, I'll close the issue once I release the update.