I don't know how, but its the Grid.

If I remove

        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="1" />
        </Grid.ColumnDefinitions>
        <Grid.RowDefinitions>
            <RowDefinition Height="50" />
            <RowDefinition Height="*"/>
        </Grid.RowDefinitions>

it stops reseting to 30.......

WHY?  whats wrong with putting the control in a grid?

I’m trying reproducing it with:

<Grid x:Name="LayoutRoot" Width="400" Height="400">

        <Grid.ColumnDefinitions>

            <ColumnDefinition Width="1" />

            <ColumnDefinition Width="*" />

        </Grid.ColumnDefinitions>

        <Grid.RowDefinitions>

            <RowDefinition Height="50" />

            <RowDefinition Height="*"/>

        </Grid.RowDefinitions>

        <igTimeline:XamWebTimeline x:Name="Timeline"

                                   Grid.Column="0"

                                   Grid.Row="1"

                                   Canvas.ZIndex="99"

                                   Margin="0" 

                                   Grid.ColumnSpan="15">

        </igTimeline:XamWebTimeline>     

    </Grid>

…

public MainPage()

        {

            InitializeComponent();

            DateTimeAxis axis = new DateTimeAxis();

            axis.ShowLabelsInPreview = true;

            axis.ShowMajorGridLines = true;

            axis.ShowMinorTickMarks = true;

            axis.ShowThumb = true;

            axis.Minimum = DateTime.Now;

            axis.Maximum = DateTime.Now.AddHours(10);

            axis.AutoRange = false;

            axis.Unit = 1;

            axis.UnitType = DateTimeUnitType.Hours;

            axis.ScrollScale = 0.01;

            axis.ShowLabels = true;

            axis.ScrollPosition = 0.5;

            this.Timeline.Axis = axis;

        }

This is still working. Can you send us your project with the Timeline as attached project here?