i attempted to upgrade gsap version at work and implement a tween of some css variables and immediately found an problem in chrome version 49 which i have personally already bumped into, and not sure what other browsers this could also branch to. to be clear, this is a problem in chrome, but the workaround is easy enough you might want to incorporate it into gsap. in chrome 49 when calling `setProperty` on a css variable that is already declared, rather than replacing the old value, it is added to the element. so throughout the course of a tween, a css variable is then defined on an element many times, which the latest one is always the overriding winner, but there seems to be some performance hits associated with this as well as timing effected. teh known workaround is to call `removeProperty` before calling `setProperty` again. go ahead and try out the jsfiddle in chrome 49 and watch the inspected markup as you click around.