The following error was encountered when building after setting csDropDownList while using TTMSFNCComboBox in TMS Web Core environment.
I request you technical support.
From your description it looks like either WEBLib.StdCtrls or Vcl.StdCtrls (or both) is after VCL.TMSFNCComboBox/WEBLib.TMSFNCComboBox in the uses clause. Can you make sure to have them before VCL.TMSFNCComoBox/WEBLib.TMSFNCComboBox?