Firefox Rich Text Editor Bug?

I’m working on a blog in Firefox for both OS X and Windows. I use the rich text editor, but I find that it has very strange behavior. I don’t know if this qualifies as a real bug, but it doesn’t happen in IE, so I’m posting it here. When I have a good deal of text and images in a post, everything is working fine until I try to backspace over a br/ when I do, the view jumps up a full page, and stays up there, until I start deleting text. This makes it nearly impossible to edit things, and makes me constantly scroll down, until I inevitably have to erase a space again.

This is made doubly difficult by the fact that single carriage returns look like double spaces while I am typing, but then once I publish and return to the blog, double spaces often disappear or look like half spaces. Is there any way to make the rich text editor fall more closely in line with what my posts look like? For now it’s an awful lot of guess work, and feels very buggy.

for reference, my blog is https://www.beninbrooklyn.com/

Thanks!