I have run into an issue with edit forms in SharePoint 2013. When opening the form in a modal dialog and clicking the "Show More" button, there is no vertical scrollbar and no way to scroll down the form to finish it. This issue is present in IE and Chrome, but not in Firefox. It started happening after upgrading our 2010 site to 2013, but I was able to reproduce it in my dev 2013 site as well.
So far I have found that it looks like it might be a problem with the autoSize function that SharePoint uses in the edit form javascript, in the rlfiShowMore() function, but I haven't verified that yet as I don't know how to edit that code to test.
Has anyone else seen this or something similar? The closest other issue I found was http://social.technet.microsoft.com/Forums/windows/en-US/63b96275-a13c-4981-aa89-58b023784ae7/sharepoint-2013-javascript-errors-when-editing-list-items-in-dialog, and I do get those errors too (and the solution does not work for me either).