"Sequencer: When using an animBP there's no animation at all (preview) without an animation in the animation track. Strangely enough the animation BP starts running if you add any animation to the animation track (even though the specified animation doesn't actually play). It is always running though even when the sequence is paused and you can't preview/scrub what the actual animation would look like. It's also possibly to break this by changing the mesh and anim BP using a construction script (using run each frame), ending up with an animation in the anim track that isn't compatible with the active skeleton. This turns all of the meshes red in the view to left and they stop animating.
Ideally (for me) it should act as if frame 0 is the frame 0 in game time (as if pressing Play), play back normally when playing back the sequence, don't play back automatically when the sequence is not running, and support scrubbing (evaluating the anim BP for the frame time in the sequence). "
Result: Animation set in AnimBP is played only when animation track is added and plays on loop (unable to scrub)
There's no existing public thread on this issue, so head over toAnswerHub just mention UE-72209 in the post.