I just found this post from last December about this issue, also:
This was reported as a bug (http://world.episerver.com/support/Bug-list/bug/CMS-1503), but it's currently marked as "Won't fix." I'm also having trouble with this bug.
I've encountered these issues too. We opted for a second style sheet that is rendered in the _layout.cshtml when the user is in either edit or preview mode. In these cases we've added additional styles for specific blocks to fix the height issue. It might be a bit cleaner than your interim solution.
This is odd behavior I found in migrating our existing site over to EPi and it causes the editor to infinitely increase in height. We are on update 121 (installed today in the hopes that it would fix the issue).
Steps to reproduce:
Here's the source of the rendered page:
Here's the block view:
Here's a screenshot of the rendered html in the editor in Chrome's Dev Tools. The purple items are incrementing infintely.
https://twitter.com/jayburling/status/756558818478174208/photo/1
I'm going to try to work around this by adding a style to set the height in edit mode to a set pixel size, but obviously would prefer not to have to. :)
Update: Here's my terrifically bad patch/hack so that I can edit these pages without the editor exploding:
Thanks!
Jay Burling
burling@hendrix.edu