I have a page with a few links and images included. It's nothing fancy or crazy, just a simple page. However, for some reason I can't fathom, it seems to randomly not process Markdown. It does it to the extent that even code I've copied and pasted from elsewhere on the page doesn't work.
For example I have:

Which works like a charm. I decided to move it into a grid instead of floated right and slightly lower down the page so ended up with this:
<div class="col s4">

</div>
That removed the link highlighting in the admin editor and when I viewed the saved page, I just see the markdown, not the image. I changed the actual image back to the original link and still no image showed.
I did wonder if the highlighting meant that I had a flaw in the syntax, however deleting the whitespace/indentation made the editor highlight as you'd expect, but the saved page still displays the raw markdown. I have also edited the page in vi to ensure that the editor isn't the issue, but still unprocessed markdown.
I have a link which acts similarly. It is processed fine as part of a sentence, however when I copy and paste it elsewhere the whole thing is just unprocessed.
I can't understand why the same syntax on the same page is processed sometimes but not others. I am clearing the cache between saving and viewing just in case that was a bug but it makes no difference. I'm open to suggestions of tests I can try and I'm aware this could be something painfully simple I've missed so no suggestion is too obvious right now.