I recently attempted to update to EPiServer.CMS.UI >= 11.11.0, and found the content areas for on-page editing would continuously grow from resizing to match content.
Upon investigation, one of the chief things that changed was the addition of epiEditMode.css and the rules:
transition: all 0.3s linear;
The fix is easy though, I just had to override these rules with the following:
Understandably a CSS rule on * is a bad idea, but width or height transition rule on DIV makes a reasonable amount of sense. I figured this might be helpful to others encountering similar problems.
All I did was to set the min-height: 14px; to min-height: 14px!important; and it worked for me, I haven't seen anything else affected by it