Xaml controls don't show up - ios

Question

I have a Xamarin.Forms app with FreshMvvm. Some of its users experience a problem on their iPhones. A page comes up empty. Here is how the page would look with a simulated exception:
All static xaml stuff is there, including labels. But our customers see this instead:
In the ScrollView, only the BoxViews with height = 1 that make those horizontal lines, are there. And no labels.
Here is my xaml:
<ContentPage
xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
x:Class="LATICRETE_MobileApp.Pages.CoverageCalculator.CoverageCalculatorResultsPage"
ControlTemplate="{StaticResource MainPageTemplate}"
xmlns:controls="clr-namespace:LATICRETE_MobileApp.Controls"
Title="Coverage Results" >
<ContentPage.Content>
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="4*" />
<RowDefinition Height="*" />
</Grid.RowDefinitions>
<ScrollView Grid.Row="0">
<StackLayout Margin="30">
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="Auto" />
<RowDefinition Height="1" />
<RowDefinition Height="Auto" />
<RowDefinition Height="1" />
<RowDefinition Height="Auto" />
<RowDefinition Height="1" />
<RowDefinition Height="Auto" />
<RowDefinition Height="22" />
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*" />
<ColumnDefinition Width="*" />
</Grid.ColumnDefinitions>
<Label Text="Tile Size:" FontAttributes="Bold" Grid.Row="0" Grid.Column="0" />
<Label Text="Tile Thickness:" FontAttributes="Bold" Grid.Row="2" Grid.Column="0" />
<Label Text="Joint Size:" FontAttributes="Bold" Grid.Row="4" Grid.Column="0" />
<Label Text="Trowel Size:" FontAttributes="Bold" Grid.Row="6" Grid.Column="0" />
<Label Text="{Binding TileSize}" Grid.Row="0" Grid.Column="1" />
<BoxView BackgroundColor="Gray" Grid.Row="1" Grid.ColumnSpan="2" />
<Label Text="{Binding TileThickness}" Grid.Row="2" Grid.Column="1" />
<BoxView BackgroundColor="Gray" Grid.Row="3" Grid.ColumnSpan="2" />
<Label Text="{Binding JointSize}" Grid.Row="4" Grid.Column="1" />
<BoxView BackgroundColor="Gray" Grid.Row="5" Grid.ColumnSpan="2" />
<Label Text="{Binding TrowelSize}" Grid.Row="6" Grid.Column="1" />
<BoxView BackgroundColor="{StaticResource LaticreteColor}" Margin="0,10,0,10" Grid.Row="7" Grid.ColumnSpan="2" />
</Grid>
<Label Text="{Binding Adhesive}" FontAttributes="Bold" />
<Label Text="{Binding AdhesiveCoverage}" />
<BoxView BackgroundColor="Gray" HeightRequest="1" />
<Label Text="{Binding Grout}" FontAttributes="Bold" />
<Label Text="{Binding GroutCoverage}" />
<BoxView BackgroundColor="Gray" HeightRequest="1" />
<Label Style="{StaticResource LabelParagraphStyle}" Text="*Calculated coverage indicated is approximate, based on nominal tile size and is provided for purposes of estimation only." />
<Label Style="{StaticResource LabelParagraphStyle}" Text="Actual grout coverage will vary depending on jobsite conditions, actual tile size and installed grout joint size. Use of sufficient thin-set reduces grout requirement." />
<Label Style="{StaticResource LabelParagraphStyle}" Text="Add 10% to coverage estimates for waste, spillage and clean-up. Add 10%-15% to grout coverage estimate when grouting unglazed quarry tile." />
<Button
Text="{Binding ButtonShareText}"
Command="{Binding ShareCommand}"
Style="{StaticResource ButtonStyle}"
FontSize="Large"
HorizontalOptions="CenterAndExpand" />
</StackLayout>
</ScrollView>
<controls:Toolbar
ButtonCalculatorIcon="{Binding ButtonCalculatorIcon}"
ButtonDistributorLocatorIcon="{Binding ButtonDistributorLocatorIcon}"
ButtonScanQRCodeIcon="{Binding ButtonScanQRCodeIcon}"
ButtonVideoCallIcon="{Binding ButtonVideoCallIcon}"
ButtonMoreIcon="{Binding ButtonMoreIcon}"
CalculatorCommand="{Binding CalculatorCommand}"
DistributorsLocatorCommand="{Binding DistributorsLocatorCommand}"
ScanQRCommand="{Binding ScanQRCommand}"
VideoCallCommand="{Binding VideoCallCommand}"
MoreFeaturesCommand="{Binding MoreFeaturesCommand}"
ShowVideoChat="{Binding ShowVideoChat}"
ControlTemplate="{StaticResource ToolbarTemplate}"
Grid.Row="1" />
</Grid>
</ContentPage.Content>
On App Center Diagnostics, I could see exceptions like this:
I don't know if this causes our issue, but that is the only thing I could find.
Also, on the same iPhone models some users have this issue, and others don't. I personally could not reproduce it on my phones.
ADDED:
The code-behind constructor and the pagemodel constructor contain almost nothing:
public CoverageCalculatorResultsPage ()
{
InitializeComponent ();
}
...
public CoverageCalculatorResultsPageModel()
{
ScreenName = "Coverage Results";
ShareCommand = new Command(async () => await Share());
}
Pagemodel's Init():
public override void Init(object initData)
{
try
{
base.Init(initData);
throw new Exception("Test Exception: remove when done");
_previousModel = (CoverageCalculatorPageModel)initData;
// Standard units
string lengthUnits = "\"";
string coverageUnits = " Ft²";
double tileWidth = Convert.ToDouble(_previousModel.TileWidth, CultureInfo.InvariantCulture);
double tileHeight = Convert.ToDouble(_previousModel.TileHeight, CultureInfo.InvariantCulture);
double jointWidth = Convert.ToDouble(_previousModel.SelectedJointSize.Key, CultureInfo.InvariantCulture);
double tileThickness = Convert.ToDouble(_previousModel.SelectedTileThickness.Key, CultureInfo.InvariantCulture);
if (_previousModel.SelectedUnit.Code == UnitCode.Metric)
{
lengthUnits = "mm";
coverageUnits = "M²";
// Convert to standard units
tileWidth /= 25.4;
tileHeight /= 25.4;
}
// Perform adhesive calculation
// Official formula is: Coverage (Sq Ft)/Unit = (coverage_cuInPerUnit/((Trowel_Height * 0.707108)/2)) * 0.0069444
double cuInPerUnit = _previousModel.SelectedAdhesive.Coverage;
double trowelHeight = Convert.ToDouble(_previousModel.SelectedTrowelSize.Key, CultureInfo.InvariantCulture);
double adhesiveCoverage = (cuInPerUnit / ((trowelHeight * 0.559) / 2)) * 0.0069444;
// Perform grout calculation
// Official formula is: Coverage (Sq Ft)/Unit = coverage_cuInPerUnit/((Tile_Width+Tile_Height+Joint_Width)*Tile_Thickness*Joint_Width*(144/((Tile_Width+Joint_Width)*(Tile_Height+Joint_Width))))
cuInPerUnit = _previousModel.SelectedGrout.Coverage;
double groutCoverage = cuInPerUnit / ((tileWidth + tileHeight + jointWidth) * tileThickness * jointWidth * (144 / ((tileWidth + jointWidth) * (tileHeight + jointWidth))));
if (_previousModel.SelectedUnit.Code == UnitCode.Metric)
{
// Convert coverages to metric units if necessary (sqft to m2)
adhesiveCoverage *= 0.092903;
groutCoverage *= 0.092903;
}
TileSize = $"{_previousModel.TileWidth}{lengthUnits} x {_previousModel.TileHeight}{lengthUnits}";
TileThickness = _previousModel.SelectedTileThickness.Value;
JointSize = _previousModel.SelectedJointSize.Value;
TrowelSize = _previousModel.SelectedTrowelSize.Value;
Adhesive = _previousModel.SelectedAdhesive.Name;
AdhesiveCoverage = $"Adhesive Coverage per Unit*: {adhesiveCoverage: #.##}{coverageUnits}";
Grout = _previousModel.SelectedGrout.Name;
GroutCoverage = $"Grout Coverage per Unit*: {groutCoverage: #.##}{coverageUnits}";
}
catch(Exception ex)
{
HandleException(ex, true);
}
}
All the data is obtained from the user on the previous page or from the calculations shown above.