IssueTracker

Could be related to the changes you've made in FixedFragmentStateAdapter. Could you share the code, I can have a quick look.

> Could be related to the changes you've made in FixedFragmentStateAdapter. Could you share the code, I can have a quick look.

Sorry, but I believe that is not a culprit. I just added a single line of code to avoid BadParcelableException.

https://issuetracker.google.com/issues/132840199

```
    @Override
    public final void restoreState(@NonNull Parcelable savedState) {
        if (!mSavedStates.isEmpty() || !mFragments.isEmpty()) {
            throw new IllegalStateException(
                    "Expected the adapter to be 'fresh' while restoring state.");
        }

        Bundle bundle = (Bundle) savedState;
        bundle.setClassLoader(getClass().getClassLoader()); // <-- ADDED THIS LINE

        for (String key : bundle.keySet()) {
          ...
    }
```

I investigated the issue and turned out the part of the scenario which causes the problem;

1. RecyclerView.recycleViewHolderInternal()
2. hodler.doesTransientStatePreventRecycling() retuns true
3. FragmentStateAdapter.onFailedToRecycleView() -> onViewRecycled() -> removeFragment()
4. onFailedToRecycleView() retuns false, it means the ViewHolder is not recycled yet.
5. Soon after, FragmentStateAdapter.onViewAttachedToWindow() -> placeFragmentInViewHolder() ->  IllegalStateException("Design assumption violated.")

Hi! I have successfully created a demo project which can reproduce this issue. Please check the following repo and I hope it helps to resolve the issue.

https://github.com/h6ah4i/FragmentStateAdapterOnFailedToRecyclerViewFailure

[UPDATE]
This issue still exists on ViewPager2 v1.0.0-alpha06 with RecyclerView v1.1.0-beta01.