Hi Moustafa,
Most probably you have a javascript function in your user control say some client-side event handler. In such case when you add the control twice both client-side events will be served by the last javascript function (because it will override the one from the first control). If this is the case you should make sure that the name of the javascript routine is unique by appending some unique identifier - e.g. the ClientID property of the user control. Here is some example:
UserControl1.ascx:
function MyFunction_<%= ClientID%>()
{
}
UserControl1.ascx codebehind:
MyControl1.OnClientEvent = "MyFunction_" + ClientID;
Regards,
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