A workaround is to disable the embedded jQuery and use an older version (for example, 1.11.1 which is the previous version the suite used): https://docs.telerik.com/devtools/aspnet-ajax/controls/scriptmanager/disabling-the-embedded-jquery

Repro steps:

- add the dropdown
- write something

expected: you see the suggestions

actual: the suggestions go off the screen to the left



        <telerik:RadAutoCompleteBox ID="companyNameSelector" runat="server"
            EnableDirectionDetection="true" EnableScreenBoundaryDetection="true" DropDownWidth="400px"
            Width="200px">
        </telerik:RadAutoCompleteBox>



    protected void Page_Load(object sender, EventArgs e)
    {
        companyNameSelector.DataTextField = "someColumn";
        companyNameSelector.DataSource = GetDummyData();
        companyNameSelector.DataBind();
    }



    protected DataTable GetDummyData()
    {
        DataTable tbl = new DataTable();
        tbl.Columns.Add(new DataColumn("id", typeof(decimal)));
        tbl.Columns.Add(new DataColumn("Name", typeof(string)));
        tbl.Columns.Add(new DataColumn("moreData", typeof(decimal)));
        tbl.Columns.Add(new DataColumn("someColumn", typeof(string)));
        tbl.Rows.Add(new object[] { 1, "one", 2, "firstRecord4" });
        tbl.Rows.Add(new object[] { 2, "two", 3, "secondRecord4" });
        tbl.Rows.Add(new object[] { 3, "three", 4, "thirdRecord4" });
        tbl.Rows.Add(new object[] { 98, "four", 5, "fourthRecord4" });


        return tbl;
    }