@finnj, I know ??
@lisa, I just registered at your site, created a test post, then edited it. I can replicate the issue you’re experiencing.
My guess is that TinyMCE or some plugin for it (e.g. wpEditImage, wp_gallery) breaks the HTML for image.
I suggest you check TinyMCE configuration and/or PHP settings (magic quotes, stripping slashes). This StackOverflow thread might be useful.
Below is an example of what happens to HTML for inserted image – notice that http is stripped from image src attribute and there are duplicated double quotes used for image attributes (class, width and height).
Current code (breaking images):
<img class="”size-medium" alt="”Food" src="//www.foodtravelist.com/wp-content/uploads/2014/02/Food-Travelist-Pasta-Always-Pleases-300×225.jpeg”" width="”300″" height="”225″">
HTML code should look like this:
<img class="size-medium" alt="Food" src="https://www.foodtravelist.com/wp-content/uploads/2014/02/Food-Travelist-Pasta-Always-Pleases-300×225.jpeg" width="300" height="225">
Hope this helps.