FRP is like OOP. For some problems, there is a level of granularity where it's an absolute killer, and nothing gets even nearly as effective. But if you write it with too much granularity, it will completely destroy your code. (And with too little granularity, it will be useless.)

This phrase alone: "data-flows that go through multiple modules" is a very good indication that you broke things down too much, and should have ditched the FRP abstraction on a higher level.