Hi, sorry for the delays in replying to this.
We’re currently finalizing the 5.6 release so I’ll try and make sure Blocking Evaluation works again in there.
In the meantime, for 5.5, I think it might actually be a fairly simple fix if you can patch the engine code. When Blocking Evaluation is enabled on the animation, `UUMGSequencePlayer::ConstructEntitySystemLinker()` makes a standalone/private linker for this animation. There’s no need for the `SynchronousRunner` anymore because the linker (and it associated runner) can be considered and used as “synchronous”. So I think that inside `UUMGSequencePlayer::PlayInternal`, instead of checking `Runner == SynchronousRunner`, you can check `EnumHasAnyFlags(Animation->GetFlags(), EMovieSceneSequenceFlags::BlockingEvaluation)`. This would make it flush the queued animation updates immediately.