Still no joy. I have removed the RequestIDCMP code and replaced it with the proper AddEventHandler code. Still the same problem occurs. When I specify RAWKEY and VANILLAKEY events in the event handler node, string input stops working. Right and left arrow keys do still work in the strings for some reason, but typing ordinary letters in the string activates my event handler code instead. Yet it seems to work ok in MUI 3.8.

I am wondering if it is anything to do with ECX MUI modules not being compatible with MUI 4? I tried altering the event handler priority, and a number of other things. But still the same problem. Event handler code is being handled before the active object. Any ideas? Thanks for your help.