WPF TextBox doesn`t update binded source - wpf

Question

I've got a textbox with custom style and binded to it property. If i change value in textbox property doesn't changes but if property changed from code textbox updates right.
I guess it's Mode=TwoWay missing somewhere but I can't figure out where as if I clear style frm xaml it works fine.
Form xaml:
<TextBox x:Name="tbFrames" Height="27" Canvas.Left="53" TextWrapping="Wrap" Text="{Binding Path=frames, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" Canvas.Top="185" Width="64" Style="{DynamicResource StyleTextBox}" PreviewTextInput="AnimationValidationTextBox"/>
Style xaml:
<Style x:Key="StyleTextBox" TargetType="{x:Type TextBox}">
<Setter Property="Height" Value="27" />
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type TextBox}">
<Grid>
<Border
x:Name="PART_border"
Background="Transparent"
BorderBrush="#FF434346"
BorderThickness="1"
/>
<TextBox Foreground="#FFBABAC7" BorderThickness="0" Background="Transparent" Text="{Binding RelativeSource={RelativeSource TemplatedParent}, Path=Text, Mode=TwoWay}" HorizontalAlignment="Center" VerticalAlignment="Center"/>
</Grid>
<ControlTemplate.Triggers>
<Trigger Property="IsMouseOver" Value="True">
<Setter TargetName="PART_border" Property="Background" Value="#FF414146" />
<Setter TargetName="PART_border" Property="BorderBrush" Value="#FF5A5A5D" />
<Setter TargetName="PART_border" Property="Opacity" Value="0.7" />
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
INotifyPropertyChanged is implemented:
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged(string propertyName)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null) handler(this, new PropertyChangedEventArgs(propertyName));
}
And looks like working as like I`ve said before if I remove my style from control source updetes.
At first in style textbox binding was:
<TextBox Foreground="#FFBABAC7" BorderThickness="0" Background="Transparent" Text="{TemplateBinding Text}" HorizontalAlignment="Center" VerticalAlignment="Center"/>
And it doesn't worked so I've changed it to RelativeSource and TwoWay mode but there are still no result.
What can be wrong?
PreviewTextInputCode is :
private void AnimationValidationTextBox(object sender, TextCompositionEventArgs e)
{
if (!animationOpened)
{
e.Handled = true;
return;
}
NumberValidationTextBox(sender, e);
}
private void NumberValidationTextBox(object sender, TextCompositionEventArgs e)
{
Regex regex = new Regex("[^0-9]+");
e.Handled = regex.IsMatch(e.Text);
}
And property declared as:
private int _frames;
public int frames
{
get => _frames;
set
{
_frames = value;
OnPropertyChanged("frames");
}
}
And with default style frames updates both way with all this checking.