The issue reported previously - Uncaught TypeError: Cannot read properties of null (reading 'className') - is still present if setting the <compilation debug=”true”> in the web.config and EnableScriptCombine="false" in the ScriptManager.

The issue occurs when setting the Enabled property to false, which triggers a JavaScript error and causes the components to break.

Code to replicate the problem

<telerik:RadTextBox ID="RadTextBox1" runat="server" Enabled="false"></telerik:RadTextBox>