I tried some MTP files including a timer, my own or from Steve.
The timer always has effect if the test-start button is pressed, but not if the input is triggered. Same result with midi input or key stroke. So I made a simple test file, where the timer input is escape key, and the action (moving the mouse pointer to upper left corner) is triggered by the timer. Also here it works when test-start is pressed, but not when escape key is pressed. Am I missing something?