I made an animation using Adobe Animate and embedded it in a html-widget on the website, while test.html and createjs.min.js are stored locally.

html in the widget looks like this:

<iframe sandbox="allow-scripts" src=".html" width="678" height="678"></iframe>

the "test.html" starts

<!-- write your code here -->
<script src="createjs.min.js"></script>
<script>
var createjs,AdobeAn;!function(t,e){var n,i={},o={},s={};i.webFontTxtInst={};var a=0,r=0,l=[],c=......

now I realize, that this is not loaded defer. although all other iframes are loaded defer. If I add defer to the "test.html" like this...

<!-- write your code here -->
<script defer src="createjs.min.js"></script>
<script>
var createjs,AdobeAn;!function(t,e){var n,i={},o={},s={};i.webFontTxtInst={};var a=0,r=0,l=[],c=......

the animation is not loading anymore (only the background color can be seen).

Any clues how to solve this?

This is how it looks if the animation runs ;-)