repro

samples/ControlCatalog/Pages/AutoCompleteBoxPage.xaml

@@ -3,26 +3,21 @@
   xmlns:l="clr-namespace:ControlCatalog.Pages;assembly=ControlCatalog"
   x:Class="ControlCatalog.Pages.AutoCompleteBoxPage">
   <l:AutoCompleteBoxPage.Styles>
-    <Style Selector="l|AutoCompleteBoxPage[SideBarEnabled=False] Grid#sidebar">
+    <Style Selector="l|AutoCompleteBoxPage[SideBarEnabled=True] Grid#sidebar">
       <Style.Animations>
-        <Animation Duration="0:0:0.5" FillMode="Both" Easing="QuadraticEaseIn">
-          <!-- <KeyFrame Cue="0%">
-            <Setter Property="Width" Value="250" />
-          </KeyFrame>  -->
+        <Animation Duration="0:0:0.5" FillMode="Both" Easing="QuadraticEaseOut">
           <KeyFrame Cue="100%">
-            <Setter Property="Width" Value="0" />
+            <Setter Property="Width" Value="250" />
           </KeyFrame>
         </Animation>
       </Style.Animations>
     </Style>
-    <Style Selector="l|AutoCompleteBoxPage[SideBarEnabled=True] Grid#sidebar">
+    <Style Selector="l|AutoCompleteBoxPage[SideBarEnabled=False] Grid#sidebar">
       <Style.Animations>
-        <Animation Duration="0:0:0.5" FillMode="Both" Easing="QuadraticEaseOut">
-          <!-- <KeyFrame Cue="0%">
-            <Setter Property="Width" Value="0" />
-          </KeyFrame> -->
+        <Animation Duration="0:0:0.5" FillMode="Both" Easing="QuadraticEaseIn">
+  
           <KeyFrame Cue="100%">
-            <Setter Property="Width" Value="250" />
+            <Setter Property="Width" Value="0" />
           </KeyFrame>
         </Animation>
       </Style.Animations>

src/Avalonia.Animation/AnimationInstance`1.cs

@@ -119,9 +119,10 @@ namespace Avalonia.Animation
         {
             if (_fillMode == FillMode.Backward || _fillMode == FillMode.Both)
                 if (_currentIteration == 0)
-                    PublishNext(_firstKFValue);
+                    _targetControl.SetValue(_animator.Property, _firstKFValue, BindingPriority.LocalValue);
+
                 else
-                    PublishNext(_lastInterpValue);
+                    _targetControl.SetValue(_animator.Property, _lastInterpValue, BindingPriority.LocalValue);
         }
 
         private void DoPlayStates()
@@ -151,11 +152,14 @@ namespace Avalonia.Animation
             if ((_fillMode == FillMode.Backward
                    || _fillMode == FillMode.Both) & indexTime == 0)
             {
-                DoDelay();
+
+                _targetControl.SetValue(_animator.Property, _neutralValue, BindingPriority.LocalValue);
+                return;
             }
             else if (indexTime > 0 & indexTime <= initDelay)
             {
                 DoDelay();
+                return;
             }
             else
             {