robwebb364's post in animation pausing unwanted was marked as the answer
OK I think I have solved the first part of this.
As I am using 'yoyo' it is not necessary to put in the parts of the animation which take the opacity of each element in turn back to zero
- GSAP does that for me.
The code on dropbox is now modified and appears to work without pause.
thanks for commenting
[ im not sure the time randomisation is working, will post separately]