Error: while dragging the handler, the level editor viewport is not updated with the current curve that is being edited. Actually, it’s even worse: it does not update even after release the mouse button. The curve is only updated after change the value of some key (or in the moment of the fist click and movement of a handler).
I’m actually surprised I can’t find anyone talking about this issue. It’s not severe, but It makes the animation workflow almost impossible to deal with.
I have gone ahead and followed your steps to reproduce the issue. Upon adjusting the curves in sequencer and either scrubbing back through the track or playing it(in sequencer), the results of changing the curves are visible in the editor. Are there any steps that I may be leaving out to not be seeing the same issue? If you can send me some screen shots/gif/or sample project I can look into this more.
I made a movie showing the issue. The video has some weird artifacts, but I think it is good for demonstration purposes. Notice that the viewport doesn’t update while I’m dragging the handlers and neither when I release the mouse button: Unreal Engine - Sequencer issue - YouTube
There is no additional steps, I can reproduce the issue even on a blank project. I’m using Windows 10 and the issue also happens on UE 4.18.
Thank you for bringing this to our attention. It does not look like this is something that is a part of sequencer right now. For a workaround try adjusting the curve a little at a time and then clicking in the editor viewport to update the curve in there. This should show you the newest direction of the curve and play correctly. I have gone ahead and submitted a feature request for the viewport to auto update as you change the curves. This would allow the user to work in a more real-time style environment and improve workflow. If you have any questions regarding this thread or would like an update in the future, feel free to reopen it and I will get back to you with more information.