We have the exact same problem. We are using flex content with wysiwyg and some other fields and the backend is unusable. Scrolling will kill the browser. There is a serious issue with the JS in the ACF version. We are using pro btw.
Could the developers please have a look at this.
At the moment, the plugin is not scalable for bigger, more complex environments. We would love to use ACF for future projects, but this really concerns me.
