Fix storyboard animations not starting their animation playback from the correct point in time

osu.Game/Storyboards/Drawables/DrawableStoryboardAnimation.cs

@@ -10,6 +10,7 @@ using osu.Framework.Graphics;
 using osu.Framework.Graphics.Animations;
 using osu.Framework.Graphics.Textures;
 using osu.Framework.Utils;
+using osu.Game.Screens.Play;
 using osu.Game.Skinning;
 using osuTK;
 
@@ -115,6 +116,21 @@ namespace osu.Game.Storyboards.Drawables
             Animation.ApplyTransforms(this);
         }
 
+        [Resolved]
+        private IGameplayClock gameplayClock { get; set; }
+
+        protected override void LoadComplete()
+        {
+            base.LoadComplete();
+
+            // Framework animation class tries its best to synchronise the animation at LoadComplete,
+            // but in some cases (such as fast forward) this results in an incorrect start offset.
+            //
+            // In the case of storyboard animations, we want to synchronise with game time perfectly
+            // so let's get a correct time based on gameplay clock and earliest transform.
+            PlaybackPosition = gameplayClock.CurrentTime - Animation.EarliestTransformTime;
+        }
+
         private void skinSourceChanged()
         {
             ClearFrames();

osu.Game/Storyboards/StoryboardSprite.cs

@@ -26,7 +26,7 @@ namespace osu.Game.Storyboards
 
         public readonly CommandTimelineGroup TimelineGroup = new CommandTimelineGroup();
 
-        public double StartTime
+        public virtual double StartTime
         {
             get
             {
@@ -54,6 +54,14 @@ namespace osu.Game.Storyboards
                         return firstAlpha.startTime;
                 }
 
+                return EarliestTransformTime;
+            }
+        }
+
+        public double EarliestTransformTime
+        {
+            get
+            {
                 // If we got to this point, either no alpha commands were present, or the earliest had a non-zero start value.
                 // The sprite's StartTime will be determined by the earliest command, regardless of type.
                 double earliestStartTime = TimelineGroup.StartTime;