Thanks PointC. I guess I should examine the docs first on things like this but the intro for 1.19.0 download at the bottom just takes you direct to the TweenMax build so I assumed it was included in the Max build.
I followed your advice stripped out the tweens till I isolated the problem. Huge DUH!! on my part I was missing a decimal - I had 125 instead .125 as a time offset on one of the tweens. Pretty dramatic difference. The animation it was attached to was very subtle so I wasn't noticing the problem.
Only a couple of days in with Gsap but this platforms already blowing my mind. Need to keep a closer watch on my code though.