Using UDPaper breaks UDStepper Layout

Product: PowerShell Universal
Version: 4.2.12

I would like to have a light backgound behind the Stepper, so i simply used Paper.
Using Paper breaks the Stepper Layout.


And here is my code:

New-UDPaper -Elevation 0 -Content {
    New-UDStepper -Id 'stepper1' -Steps {
        New-UDStep -OnLoad {
            New-UDElement -tag 'div' -Content { "Step 1" }
            New-UDTextbox -Id 'txtStep1' 
        } -Label "Step 1"
        New-UDStep -OnLoad {
            New-UDElement -tag 'div' -Content { "Step 2" }
            New-UDElement -tag 'div' -Content { "Previous data: $Body" }
            New-UDTextbox -Id 'txtStep2' 
        } -Label "Step 2"
        New-UDStep -OnLoad {
            New-UDElement -tag 'div' -Content { "Step 3" }
            New-UDElement -tag 'div' -Content { "Previous data: $Body" }
            New-UDTextbox -Id 'txtStep3' 
        } -Label "Step 3"
    } -OnFinish {
        New-UDTypography -Text 'Nice! You did it!' -Variant h3
        New-UDElement -Tag 'div' -Id 'result' -Content {$Body}

Can you tell me how to fix the layout?

Kind Regards