You can use the
ClientIDMode="Static"
attribute on the control (DropDownList), which ensures that the client ID remains the same as the server ID.
<asp:DropDownList runat="server" ID="drdInstructionCode" ClientIDMode="Static">
</asp:DropDownList>
This approach should help you avoid issues related to varying client IDs in different server environments. Also see the link to explore this feature
https://www.codeproject.com/Articles/34151/ASP-NET-4-0-Client-ID-Feature