When you press the button how fast does the light blink? This is the maximum event rate that you remote supports. It can be that we are limited here.
Now lets try this:
turn off the Generate Girder REPEAT/OFF Event Modifiers option in the USB-UIRT. I remember seeing some funny business there.
Just for testing purposes delete all your mappings in the mapping editor ( export/save them first if you need them).
Add a Mapping device
Add a Output Event. Set this to PLAY
Add and learn 1 input event.
Select the output event (PLAY) again and check Generate Repeat Release. Set the repeat delay to 100ms.
Hit the button on the remote, look at the logger. Do you see the play event come by? If you hold the button does the play event show the repeat modifier?
No support through PM