draggableScrollableController not attached to a sheet after it has been attached

Question

I'm trying to use a DraggableScrollableSheet inside a BlocBuilder so that when I navigate to a page I can do something like this:

cubit.draggableScrollableController.animateTo(
    .5, // or 1.0
    duration: Duration(seconds: 10),
    curve: Curves.easeInOut);

and it will hopefully scroll nicely to the correct height for whatever particular page the user is on.

Anyway, I was trying to test this out so I put in the .animateTo function directly after it was attached to the DraggableScrollabelSheet but I get an error stating:

_AssertionError ('package:flutter/src/widgets/draggable_scrollable_sheet.dart': Failed assertion: line 170 pos 7: 'isAttached': DraggableScrollableController is not attached to a sheet. A DraggableScrollableController must be used in a DraggableScrollableSheet before any of its methods are called.)

return BlocBuilder<FrontPageContainerHeightCubit,
            FrontPageContainerHeightCubitState>(
        builder: (context, state) => Container(
            alignment: Alignment.bottomCenter,
            child: DraggableScrollableSheet(
                initialChildSize: services.screen.frontPageContainer
                    .asPercentage(state.frontPageContainerHeight),
                minChildSize: services.screen.frontPageContainer
                    .asPercentage(state.frontPageContainerHeight),
                maxChildSize: min(
                    1.0,
                    max(
                        services.screen.frontPageContainer
                            .asPercentage(state.frontPageContainerHeight),
                        services.screen.frontPageContainer.maxPercentage)),
                controller: cubit.draggableScrollableController, // <--- attached
                builder: (context, scrollController) {
                  cubit.setScrollableController(scrollController); 
                  cubit.draggableScrollableController.animateTo( // <--- test
                      services.screen.frontPageContainer.asPercentage(
                          services.screen.frontPageContainer.midHeight),
                      duration: Duration(seconds: 10),
                      curve: Curves.easeInOut);
                  return Stack(
                    alignment: Alignment.bottomCenter,
                    children: [const FrontDrop(), utilities.beamer.front()],
                  );
                }))

Now, I think this is failing simply because its happing inside the same build function. but it made me question the entire attempt. Is this the right way to achieve my goal?