e:Reducer reacting to an action it doesn't listen to

Question

I have an action FETCH_HABITS_SUCCESS that's called with the right data:

but it affects a reducer that isn't listening to it:

Dates reducer doesn't listen to FETCH_HABIT_SUCCESS. The data shown in the diff from the previous image should be the one from UNMARK_SUCCESS (two actions later in the execution timeline).

For some reason, the UNMARK_SUCCESS action real modifications take place when FETCH_HABIT_SUCCESS is called, at least that's what the dev tools show. I have checked that all my reducers don't mutate state. I always make a copy of the state. People at Reactiflux have checked that I don't mutate state too.

Code:

dates reducer: https://www.pastiebin.com/5a03538e98322 habits reducer:

export default function habits(state = {}, action) {
   const newState = { ...state };
   switch (action.type) {
     case 'FETCH_HABITS_SUCCESS':
       action.habits.forEach(habit => { newState[habit.id] = habit; });
       return newState;
     case 'ADD_HABIT_SUCCESS':
     case 'EDIT_HABIT_SUCCESS':
       newState[action.habit.id] = action.habit;
       return Object.assign({}, state, newState);
     case 'DELETE_HABIT_SUCCESS':
       delete newState[action.habit_id];
       return newState;
     default: return state;
  }
}

Does anyone have any idea of what may I be doing wrong?