problem with signals in nested timelines

setup:
i have a project with nested timelines on GameObjects 3 levels deep:
parent(child(grandchild1, grandchild2)
the grandchildren have signal markers that send a signal to it's signal receiver which calls PayableDirector.Pause on the Parent.

the parent has an event trigger that sends it PlayableDirector.Start when a canvas gets a PointerClick

how it should work:
the timelines should play until a signal marker pauses the parent timeline and restart when the user clicks the display.

the problem:

This works as i expected for grandchild1, but when the timeline gets to grandchild2, after the first signal marker, the the signal is continualy retriggered every few frames.

i have made a sandbox project containing nothing else to illustrate this problem
https://drive.google.com/file/d/1u4SSiwy05diWoLhHzhaIcazqmg2O8kso/view?usp=sharing

 

thanks, that sorted it.