This is a weird bug, but our QA team noticed that quickly typing A LOT of letters (with numbers in between them) into a NumericUpDown box, freezes the UI (and it never goes back). The NumericUpDown is directly bound to VM and we are not using any converters or code behind. We are using noXaml dlls.
XAML
<telerik:RadNumericUpDown HorizontalAlignment="Stretch"
AutomationProperties.AutomationId="FindSiteBasePortNumericUpDown"
Maximum="65534"
Minimum="1"
Value="{Binding Port, Mode=TwoWay}"
IsEnabled="{Binding IsFormIdle}"/>
VM:
public Decimal Port
{
get { return m_port; }
set { SetValue_(ref m_port, value, () => Port); }
}