I'm pretty sure there is a memory leak.
I've been running an animation over the past year that was created with Animate 2019. The createjs version then was 2015. Just last week I decided to give Animate 2020 a whirl. There aren't many differences that I noticed, being in a hurry, but one difference I did notice; it does stick out. 2020 exports the createJS 1.0.0 library.
My animation contains a button to speed up or slow down the framerate. You can see the framerate in a little box in one corner. Under createJS 2015 it was possible to run the animation for hours and hours at the top speed of 60 fps. With the current 1.0.0 createJS version, however, the speed drops off dramatically within minutes. 60, 55, 50, then 40. ...
I really would like to blame my script and to find a script workaround that solves the issue, but plugging a memory leak is very hard to do on your own. Sorry for the bad news.
My civil advice to Adobe is to offer 2015 as well as 1.0.0 for export in Animate CC. CreateJS 1.0.0 is possibly flawed.
Thank you, Adobe! ! Switching to createJS 1.0.0 in Animate CC is like driving a new car.
As it happens, there was a nested enter frame function in my code. Left over from ActionScript. 1.0.0 exposed it, the source of my memory leak.
As a result of 1.0.0, the animation runs more smoothly now, than ever.
Thank you so much.