When opening a new tab in Google Chrome, the focus will sometimes (and only sometimes) not be on the address bar, which instead contains the text chrome://new-tab-page-third-party/:
When this happens, the DuckDuckGo logo (I use their new tab page) does not load as normal either, and only my 'most visited sites' appear.
The problem first started appearing a few weeks ago. I can't find any rhyme or reason in when it occurs and when it doesn't, and cannot replicate it reliably. It just happens sometimes.
prashant's answer to this question by dialex does NOT solve the issue - I already have the bookmarks bar enabled as standard, and the problem still occurs.
Why does this happen, and what can I do to address it?
EDIT: in response to a comment by user1686, this is my empty chrome://policy page: 
