This either falls under bug-fix or new development to the HTML form field. Essentially it has a height and width value that can be set, but somewhere along the line in DNN (probably the updates to new editors and/or style), it no longer obeys the height/width set in the form field.

We normally get around this problem by getting the ID of the div and of the table that the editor is rendered in and force a width that way, but it's a manual process and a bit of a nuisance to have to remember to do.

Could you look at why the attributes of the tag are not being enforced?